Do you have to be severely abused as an excuse for stupidity and fuckery? I'm not saying her gullibility and lack of self esteem may've not resulted from some sort of abuse, physical or otherwise, but I almost feel like you're slyly pointing the finger at the guy. Perhaps, I'm misunderstanding.
Either way, zero excuse for what this woman is doing if this is all true. If you're in an unhappy relationship, get the fuck out. Don't start abusing your spouse in various ways, as well. Be an adult.