Wanda Neal worked at the Pinelake Health and Rehabilitation Center in Carthage where Stewart went on a killing spree on March 29, 2009.
Stewart, 47, has admitted he was the shooter. He faces eight counts of first-degree murder - one for each of the seven elderly patients and the nurse he gunned down at the home. Three others were injured - including a Carthage police officer who ultimately stopped Stewart by shooting him in the chest.
Prosecutors are seeking the death penalty. They say he went to the nursing home looking for his estranged wife.
Neal took the stand Tuesday morning after Moore County Superior Court Judge James Webb ruled Monday that attorneys will be allowed to bring up her medical records. Stewart's defense attorneys had questioned Neal's competency after she was hospitalized for a suicide attempt.
In court Tuesday, Neal said she took 60 Xanax, Ambien, and alcohol on the eve of the trial and woke up at Moore Regional Hospital. She said she's currently under medical care for the continuing nightmares she's experienced since the mass shooting.
Neal also described to the jury Tuesday how she met Stewart and the abuse she encountered while the couple were dating and married.
She says he slapped her in high school during an argument at their homecoming dance, but they eventually married a year later.
Neal said when she attended community college and he found out she kissed another man, she says Stewart forced her to take him to campus to track down and beat up that other man. They later divorced after a year-and-a-half of marriage.
She later reconnected with Stewart after three other failed marriages.
Neal told the courtroom that Stewart left his wife of 14 years for her and the two moved in together and remarried in 2003.
Neal said she and Stewart drank daily, but she later "cut back on drinking," while his fluctuated.
Prosecutors asked Neal if she tried to leave Stewart before finally leaving on March 14 2009.
"No, I was tired of being a failure," she said. "The past marriages and everything, I wanted it to work. I guess I felt like I deserved what I was getting because I went back, but I wanted to make it work."
Witnesses have testified that Stewart called friends and said this would be the last time Neal would leave him. Notes found at his house detail how he wanted his life to end.
"I just knew. When they said somebody was in the building with a gun, I just knew it was him," Neal testified.
Neal's testimony could be important in helping prosecutors establish Stewart's state of mind in the weeks before the massacre.
Stewart's attorneys have said that he was prescribed a dangerous mix of too many sleeping pills and anti-depressants, and that he didn't know what he was doing and doesn't remember the shooting.
Meanwhile, one juror has been dismissed for medical reasons. One of the alternates have taken over their spot.