They both fucked up. She seems the type with insecurity issues & low self esteem.
He is a dickhead clown for seeing that & taking advantage of it. If you love someone, you don't treat them like shit to make yourself feel better.
It's for the best that she divorces him & cuts all ties. They don't have kids, so she is lucky.
but I'll bet my ass she will stay with him. That whole self esteem thing can really ruin lives