For more than two decades crime writer Patricia Cornwell has dramatised the life of a fictional medical examiner in her bestselling books. Now she is witnessing her own personal drama unfold in court.

Cornwell, a successful author through her novels about Dr Kay Scarpetta, is suing her former financial management firm and business manager for negligence and breach of contract, claiming they cost her and her company millions in investment losses and unaccounted-for revenues during their four-year relationship.

The Boston trial has opened a window into the life of the intensely private Cornwell, who has had to listen from the front row of the courtroom while a lawyer for the management firm described her spending habits for the jury: $40,000 (£25,000) a month for an apartment in New York City, $5m for a private jet service, $11m to buy properties in Concord, Massachusetts.

Cornwell's spouse, Staci Gruber, a neuroscientist who is an assistant psychiatry professor at Harvard medical school, spent much of the first week of the trial on the witness stand testifying about the couple's relationship with Anchin, Block and Anchin LLP, a New York accounting and wealth management firm, and Evan Snapper, a former principal in the firm.

Cornwell fired the firm after discovering in July 2009 that the net worth of her and her company, despite having eight-figure earnings per year during the previous four years, was a little under $13m, the equivalent of only one year's net income. She also claims in the lawsuit that Anchin had borrowed several million dollars, including mortgages for property and a loan for the purchase of a helicopter, and had lost millions by moving her from a conservative investment strategy to one that was high-risk without her permission.

Cornwell, 56, says problems caused by Anchin and Snapper were so distracting that they caused her to miss a book deadline for the first time in her career and cost her $15m in non-recoverable advances and commissions.

Lawyers for Anchin and Snapper deny Cornwell's claims. During opening statements at the trial, attorney James Campbell described Cornwell as "a demanding client" who "tends to push off responsibility and assign blame when things go off track".

"I do what I do when and how I do it," she allegedly wrote in an email to Snapper read by Campbell to the jury.

Anchin and Snapper claim there is no money missing from Cornwell's accounts, that any investment losses were caused by the financial and housing crisis at the time, and that the fees they charged her were reasonable for the services they provided, including everything from business management to bringing Cornwell's clothes to the tailor to arranging care for her mother.

"Where did the money go? Ms Cornwell and Dr Gruber spent the money," Campbell said. "You have to consider the large lifestyles involved, the spending habits, impulsive buying."

Cornwell, who is expected to testify during the trial, says in the lawsuit that Anchin borrowed money in her name for real estate investments ventures without telling her. She said she also found cheques written for expenses she never authorised, including a $5,000 cheque for a barmitzvah gift to Snapper's daughter from Cornwell.

Cornwell said one of Anchin's primary functions in 2006 was to ensure that locations were arranged where she could write without distraction while her home was undergoing reconstruction. She said Snapper leased a series of expensive apartments, including one at Trump Tower in New York, that she had to leave long before leases expired because of construction, privacy or other issues.

In the lawsuit, Cornwell openly acknowledges her struggles with bipolar disorder, an illness she said had contributed to her belief that she needed other people to manage her business affairs and investments. She said Anchin was aware of her illness.

"This case is, at is core, about trust," Cornwell's lawyer, Joan Lukey, told the jury. "There is no amount of money that is enough to properly compensate her for what Anchin, Block and Anchin did."

Cornwell, a former newspaper reporter, also worked for the chief medical examiner's office in Virginia before her first novel in the Scarpetta series was published in the early 1990s. During the course of her career, she has sold more than 100m books.

This isn't the first time that Cornwell's personal life has made the headlines. In the early 1990s Cornwell had an affair with Margo Bennett, a married FBI agent, which came out years later after Bennett's estranged husband was arrested and convicted for the attempted murder of his wife and the abduction of her pastor.

After Cornwell filed the lawsuit in 2009, Snapper pleaded guilty to violating campaign finance laws by buying $50,000 in tickets to an Elton John concert benefitting Hillary Rodham Clinton, using Cornwell's money. He paid a fine.

The Boston trial is expected to last about a month.