In January 2007, mob boss Sonny Corinthos hired Diane Miller to represent him. She had a reputation as a brilliant attorney with a dry wit, acerbic observations, blunt manner, and a nearly perfect courtroom record. Her top-notch trial skills worked, and, with Diane's help, Sonny once again escaped the long arm of the law.

Diane also defended Sonny's top enforcer, Jason Morgan with equal vigor whenever he landed in legal trouble. But her services weren't cheap. Diane took full advantage of Sonny's wealth, and she made no apologies.

As the years passed, Diane would take on cases outside of the mob, and time and again she prevailed on behalf of her clients. She also had her rivals, and Alexis Davis was chief among them.

In January 2008, both Diane and Alexis Davis were nominated for "Litigator of the Year." On their way to the ceremony, they were kicked off of a plane for bickering with each other and arguing with the flight attendant. They rented a car, got stuck in the middle of nowhere with a flat tire, then found trouble at a dive bar. Diane was forced to use her gun, and warned the men threatening her and Alexis that she had killed before.

On the way home from Philadelphia, after having missed the ceremony, Diane and Alexis' rental car broke down -- again. They broke into the same dive bar for shelter when they found it closed. Because it was freezing and the thermostat was out of order, they had to put on their cherished designer gowns as well as a couple of coats that they had found. They also helped themselves to beer and nuts.

Later, Diane confessed that she didn't deserve the award and, if she were to win, she would give it to Alexis. She explained that she'd once represented a man accused of raping and murdering a teenage girl because the girl had been black. He was guilty, and Diane knew she could have gotten him off, but she hadn't been able to bring herself to set a racist murderer free. Later, he was stabbed in prison, and Diane had felt that she had been partially responsible for his death. Despite her guilt, she knew that she'd done the right thing. Alexis refused to accept the award, admitting that she had killed Lorenzo Alcazar's brother, Luis, because Luis had been responsible for the death of Alexis' sister.

After Sonny's son, Michael, was shot during an attempt on Sonny's life, Diane and Alexis had drinks at Jake's. Alexis worried about her daughters, as she knew that Sonny's life endangered their safety too. Later, Diane stopped by Sonny's house to check on Max because he'd been close to the young boy. He was devastated that Michael was in a coma, and he felt guilty that he hadn't been at the warehouse to protect Michael and Sonny. When Diane opened up about her own feelings of guilt, Max and Diane found comfort in each other's arms.

Sonny was furious when he found out about Max and Diane's relationship, and he ordered them to end it, but Max stood up to Sonny and forcefully told him to back off. Sonny appeared to respect Max's refusal to back down, but Sonny made it clear that he did not want Max and Diane's private life to interfere with business.

Initially, Max and Diane tried to keep things casual because neither wanted emotional entanglements, but their feelings began to grow. When Diane discovered that Sonny, while engaged to Kate, had had a one-night stand with his ex-wife, Carly, she pushed him to be honest with Kate. After the truth was revealed, Kate forgave Sonny, but Carly and her husband, Jasper "Jax" Jacks, broke up. Max blamed Diane for Carly's misfortune because Max didn't believe that Sonny had been unfaithful, since Sonny and Kate had not been married.

Diane asked, based on Max's definition of faithfulness, if he had ever cheated on her. He answered indirectly, asking how he could have cheated, as they'd only had a casual relationship. Furious, Diane broke things off with Max. The following day, Max showed up with a boom box blasting Al Green's song, Let's Stay Together.

In October, Diane met Max's father, Maximus Giambetti. Maximus had been a mob boss until he'd been arrested and deported to Italy in 1988. The meeting did not go well. Maximus had been told that his son Max ran Sonny's empire, and Max failed to introduce Diane as his girlfriend. Instead, Max claimed that she was his attorney, so Maximus took the liberty of slapping Diane on the behind.

In 2009, After the mysterious death of Brianna Hughes in a hotel room that had been rented by Mayor Floyd, the Hughes family hired Diane to represent them in a wrongful death lawsuit. Alexis begged Diane not to take the case, but Diane ignored the request. Eventually, Alexis confided to her friend that she'd once had an affair with the mayor. As if things couldn't get worse, Alexis was arrested and charged with hit-and-run after someone ran Claudia Zacchara off the road.

Alexis suspected that Kristina might have been responsible, so Diane represented her friend, but Nikolas had worked his political connections to get Alexis sentenced to community service.

In late October, Sonny discovered that his wife, Claudia, had been responsible for Michael having been shot and put into a coma for a year. He verbally attacked Claudia at her birthday party with all of her party guests present to witness her downfall. Claudia snapped. With her back against the wall, Claudia kidnapped a very pregnant Carly Corinthos-Jacks, stole a car, and fled with her hostage. Carly was able to get away from her captor as she went into labor. She made her way to a cabin and gave birth to a baby girl, but Claudia found them and took the baby from Carly.

As Carly begged for Claudia to give the baby back, Michael approached the cabin looking for his mother. He picked up an axe handle and entered ready to defend Carly when he heard her cry out. He entered then struck Claudia in the head, killing her in an instant. Jason, Sam, Carly, and Sonny worked together to cover up the death, and Michael's involvement.

To protect Michael, Sonny confessed to the crime when Claudia's body was found, and the cause of death ruled a homicide. Diane's defense of Sonny against murder charges in Claudia's death allowed her to finally team up in the courtroom with her dear friend Alexis. The partnership took a little prodding on Diane's part, but Alexis finally saw it Diane's way and joined the defense team on Diane's terms. Once again, Diane's power of persuasion had ruled the day.

A few weeks later, Alexis was involved in a hit-and-run when she arrived home and found that her daughter Kristina had been physically abused by a boyfriend. Alexis had struck Kiefer Bauer, who had been walking along a dark road, as she had raced her daughter to the hospital. Diane informed her dear friend that, because it had been Alexis' second hit-and-run -- and the victim had died -- she would likely serve time. However, Diane was successful in keeping Alexis from serving time, but Kiefer's father had launched a civil suit.

During Sonny's contentious trial for Claudia's murder, both Diane and Alexis teamed up against prosecutor Claire Walsh, and they all engaged in ethically questionable tactics. Diane encouraged Maxie to perjure herself and knowingly accepted Carly's bogus testimony. The adults in Michael's life arranged for him to leave the country until the trial had ended. Claire assumed that Michael's testimony might incriminate Sonny, so she did everything that she could to find Michael, including taking Morgan Corinthos out of school on false pretenses to question him about his brother's whereabouts.

As the jury deliberated, Dante had tracked down his younger brother. Michael confessed to Dante the gave Dante the proof that Michael had killed Claudia -- the bloody shirt that he'd worn on that fateful night. Dante, knowing that Michael had simply defended his mother, went to court and announced that Sonny hadn't done the deed. Dante assumed that Michael would be ordered to attend counseling and given community service, but the judge was furious at what the adults around Michael had done, and decided to teach everyone a lesson, including Michael.

Michael was sentenced to five years in Pentonville with the possibility of parole after two. Diane filed an appeal, and Claire agreed to help right the injustice. Diane was desperate to get Michael out, so she helped Claire convict Jason of a crime, with the understanding that Jason would be sentenced to Pentonville and share a cell with Michael to protect him from the guards and other prisoners. Unfortunately, Jason had been too late. One night, Michael was violently raped in his jail cell.

After Dante convinced Judge Carroll to reverse his decision, the judge released Michael into the detective's custody. Frustrated that she hadn't been able to help Michael, Diane worked hard to get Jason freed. Claire agreed to let Jason out of Pentonville to pose as bait to lure serial killer Franco out of hiding.

Diane's friendship with Alexis remained steadfast through the years, and but her relationship with Max hit the rocks in 2011 when Diane co-authored a book called, The Secret Life of Damien Spinelli. Diane made plans to go on a book tour to promote her book, but Max objected. Diane reminded him that she didn't need his permission, and the two argued.

Max accused Diane of wanting to break up, prompting her to admit that she thought that they needed a break. Max hated the idea, but he recognized that it wasn't his choice. They parted on amicable terms on Feb 25, and Diane left town for a few months. When she returned, she focused on her law practice, which flourished. Diane was usually the first call for most people who found themselves in trouble. When she wasn't working, she spent time with Alexis, enjoying the finer things in life, and the occasional company of a handsome man. However, no one serious since her breakup with Max.

In September 2013, Diane made a name for herself when she successfully defended Franco against numerous murder and kidnapping charges with a brain tumor defense. Franco had been diagnosed with a brain tumor that had been removed in July. His surgeon conceded that the affected area of the brain where the tumor had been found might have triggered Franco's deviant impulses.

On December 23, Diane received the call she had dreaded for years. Max had been shot in the chest She rushed to his bedside and sat vigil until he woke up. It was touch-and-go for a bit, but Max made a full recovery and Diane remained at his side. By September 2015, they were officially back together and stronger than ever. Eventually, they moved in together.

Diane also remained a loyal friend to Alexis, and she stood by her best friend's side when Alexis' marriage to Julian Jerome fell apart, and Alexis battled alcoholism. Diane was instrumental in helping Alexis through recovery then getting Alexis' license to practice law reinstated.