sounds like "Dissociative identity disorder (previously known as multiple personality disorder) is thought to be a complex psychological condition that is likely caused by many factors, including severe trauma during early childhood (usually extreme, repetitive physical, sexual, or emotional abuse)."
Being sexually abused as a child, they act it out in adult life with many sexual encounters. Both of you need counseling, but especially her.
https://www.webmd.com/mental-health/dissociative-identity-disorder-multiple-personality-disorder#1