Dennett, who is charged with second degree murder, said she never meant to kill the elderly woman, but she said Livingstone was picking on her constantly. Dennett said it reached a point when she simply couldn't take it anymore.
She described in detail how she pushed Livingstone down a flight of stairs and then stabbed her repeatedly.
Online affair with victim's son
Dennett had been living with Livingstone and caring for her for more than a month in June 2011, when police were called to Livingstone's home and found the woman's body.
Dennett told the court on Tuesday she had come to live with the elderly woman after starting an online relationship with Livingstone's son, Robert. She thought that it was Robert Livingstone with whom she would be living, and she told the court that she came to hate him.
Outside the courtroom, Robert Livingstone reacted angrily to Dennett's testimony.
"The way I was being blamed for everything — come on, now," he said.
"I've never heard such a pack of baloney in my whole life."
The prosecution focused on how Dennett used two knives to commit the crime, walking upstairs to get a second knife after the first one broke.
Holed up in chic hotel
The court heard how after the killing, Dennett checked into the chic Nelligan Hotel in Old Montreal and spent a few days there, booking the room with Kathleen Livingstone's credit card.
By sheer coincidence, the elderly woman's friend, Sam Gaskell, happened to spot Dennett in Old Montreal and called police.
Gaskell, too, sat through Dennett's testimony on Tuesday and struggled to maintain her composure.
"It makes me sick in my heart that she's trying to explain this," said Gaskell outside the courtroom. "Kathy doesn't have an opportunity to say anything, because Kathy is gone."
The defence will present its closing arguments on Friday.Suggest a correction