SAN DIEGO (CBS 8) - We're learning more about the woman accused of killing her great aunt in her Tierrasanta home.

Tiffany Burney, 23, was arrested Saturday morning in connection with the shooting death of 74-year-old Daisy Hayes. At about the same time she was arrested, authorities searched her car, which was parked at Mercy Hospital in Hillcrest.

San Diego police have not told us what evidence they have that links Burney to the murder, but court records tell us a lot about the suspect.

By all accounts, Burney is a troubled soul.

"Supposedly she is mentally ill but I don't think that excuses anything that she did," neighbor Scott Wall said.

Wall was a neighbor and longtime friend of Daisy Hayes, who police say was shot to death by Burney last Wednesday.

"Well that was her niece. Wouldn't you open your door to your niece? I would," Wall said.

In 2006, Burney was charged with possession of marijuana and fighting in public. She served no jail time. In 2007, she was charged with burglary and grand theft, but sentenced to only eight days in jail.

Psychiatrist Mark Kalish doesn't know or treat Tiffany Burney, but says people who are mentally ill can unexpectedly turn against their loved ones.

"Very often the people that care the most are inaccurately perceived by the individual as being their tormentor," Kalish said.

In April 2010, Burney was confined to a mental health hospital after being ruled "gravely disabled." She was appointed a temporary conservator, but one month later the conservatorship was terminated.

"When people are on medication and doing well, there is no need for a conservatorship. Unfortunately some percentage stop taking their medication and they get ill again," Kalish said.

Doctor Kalish doesn't know if Burney refused to take her medication, but in December 2010, she was confined to a mental hospital again, said to be "gravely disabled" and given another conservator.

Two months later, while still "gravely disabled," she participated in outpatient psychiatric treatment. Then, just three months ago, her conservatorship was terminated again when she was ruled to be no longer gravely disabled.

Wall says Daisy was a loving person who opened her door to people in need, troubled or not.

"I think we are too easy on mentally ill people. They should be locked up and forgotten about, but that's not the way things are,"Wall said.

We talked to Tiffany Burney's mother Monday, but she refused to comment.