A lot of it doesn't make sense. From my understanding, she knew the victim and they were friends. She both claims not to remember what happened and that he stabbed her then stabbed himself.
She had a nick with a knife on her thigh and he was brutally stabbed multiple times. It appears that something sexual happened between them as when she opened the door to the police, she was naked apart from her bra. But no rape kit was done and they arrested her as a suspect.
Apparently she was very drunk at the time of the killing. The judge believes she lost her temper and killed him.