Larry Biggam, whose law firm is representing Alix Tichelman, 26, said after a court hearing that Tichelman had every reason to continue the relationship with Forrest Hayes.
"There was no intent to harm or injure Mr. Hayes," he said. "Why would she? He was a lucrative source of income to her. She appreciated the generosity and she had a motive, if any, to elongate, not end the relationship."
Biggam said Tichelman and Hayes engaged in "mutual consensual drug usage" during a sexual encounter that was initiated and encouraged by Hayes.
Police say Tichelman did not help Hayes or call 911 as he went unconscious after she administered heroin to him on Nov. 23.
Tichelman pleaded not guilty Wednesday to charges of manslaughter, great bodily injury and heroin possession. Prosecutors have said they are still reviewing the case and may bring additional, more serious charges against her.
A judge also denied her request to be released and kept her bail at $1.5 million.
Surveillance footage from the yacht shows Tichelman gather her belongings, including the heroin and needles, casually step over Hayes' body to finish a glass of wine, clean up a counter, then lower a blind before leaving the yacht, police said.
The 51-year-old father of five was found dead by the captain of his 50-foot yacht Escape the next day.
The case has prompted police in Milton, Georgia, to re-examine the overdose death of Tichelman's former boyfriend Dean Riopelle, 53, the owner of a popular Atlanta music venue. Police said a panicked Tichelman called police, saying her boyfriend had overdosed on something and wouldn't respond.
She wasn't charged in the case, and an autopsy report listed Riopelle's death as an accidental overdose of heroin, oxycodone and alcohol.
It is not clear how long Tichelman may have been involved in prostitution, though police in Santa Cruz say she had many clients in wealthy Silicon Valley.