How complicated. And how sad. Your ex seems to be a woman who can’t tolerate a “loving, good, sweet” relationship. When things get too close, she manages to fall for someone else. The excitement of new romance is a great distraction — even when it is with someone as inappropriate as someone who is in jail. I don’t think she was unhappy with your relationship. I don’t think it has to do with your children. My sense is that she can’t stand being happy in a stable relationship. The problem is with her feelings about herself.
Sadly, the answer to your question is that, yes, she can avoid having to deal with your breakup and yes, she can talk herself out of her love for you. When someone’s fear is bigger than their ability to love, they can find lots of reasons for leaving. I don’t know what happened to her that makes this make a kind of sense. I do think some counseling is needed for her to come to deal with this pattern of fleeing exactly what most women would give anything to have. I worry about you accepting her if she comes back without an agreement to get that counseling. Twice is enough for you to deal with this heartache.
I wish you well.