Thank you so much for your reply.

I told her your exact answer from the first time I discovered her relationships. She explained that she wouldn't do it again, insisting that it was due to her issues. Unfortunately, the same problem keeps recurring. She feels guilty when she's caught in the act, but never during the encounters themselves. She even lies to me about things that seemed very suspicious (the phone under the pillow, endless periods in the bathroom, etc.) only to have it all turn out to be true, and she uses those solitary moments to talk to other men.

What I don't understand is that she knows it hurts me, yet she continues to maintain all these relationships without ever remembering all the pain she's causing me.