Sheena Watters carried out the apparently motiveless attack on Alistair Green at his house in Irvine, Ayrshire, in February this year.
Watters later claimed she had no idea what happened to the 54-year old and had given him a cuddle when she discovered him bleeding.
But the victim soon told police of his ordeal leading to the arrest of the 46-year-old.
A judge heard how Mr Green - who suffered life- threatening injuries - was left so traumatised he moved out of the home he had lived in for 30 years.
Watters is now behind bars after she admitted assaulting Mr Green to the danger of his life.
She will learn her fate when she returns to the dock next month.
The High Court in Glasgow heard how Watters and Mr Green had known each other for decades and often spent time together.
Mr Green had been at his Irvine home on February 16 when Watters visited.
Judge Lord Turnbull remanded Watters in custody and deferred sentencing for reports.