Samantha Ray Mears, who was 19 at the time of the attack, entered her ex’s home while he was out. When he returned, he found her armed with a machete.
The victim later told authorities he didn’t feel as though he could escape without being hurt by Mears, who bit him on the arm.
According to reports in local news station, KPAX, Mears remained sitting on the bed armed with the knife and began arguing with him.
Court documents say she ripped some of the décor off the wall and intentionally urinated on his bed.
Mears was charged with sexual intercourse without consent, aggravated burglary, assault with a weapon, and unlawful restraint.
She must now serve 20 years in a facility in the state of Montana, over the attack in Great Falls last year.
Because the law recognises ‘rape’ as penetration, by the state of Montana’s criminal law code, Mears is guilty of sexual intercourse without consent, rather than rape.
Mears appeared in court via a video link from Montana State Hospital, and will soon be placed under the custody of a mental health facility.
Court documents reportedly state Mears suffers from a mental disease or defect.
She has also been registered as a sex offender and must complete treatment programmes and take medication.