I would not make rash decisions. I think you definitely need to share this with your therapist, please tell me you are still seeing a therapist, you should.

There could be several different reasons she is doing this. Her self esteem must have been very low for her to go so wild just by seeing you just talking with another woman. And now she is sharing that she doesn't WANT to care anymore, no love, just make it about her. I am wondering if this other guy broke it off with her and she was even more devastated so her attitude is basically F all men I am going to think about myself now and maybe that's the only thing men really want is the sex anyway. My guess is this other guy has distanced from her and her ego was hurt all over again. Her deciding to give up on having faith means she is abandoning faith and just wants to hide her hurt and is at the point where she doesn't care who she hurts while she runs away from her own hurt ego. I have a feeling her fling with this other guy was all about restoring her faith in herself that she is still attractive and has value even though you began to think about another woman, I was thinking about that when you mentioned she just had to see what this other woman looked like, that's a worry about competition and as I mentioned her sense of safety about her own value. It sounds to me like she doesn't want anyone to own her heart. She is angry and hurt still and is abandoning the entire "love" thing. This is ofcourse just a guess on my part thinking what would cause someone to behave this way.

I am curious, you mentioned there can't be anymore children, did she have something happen where she can't have children? I am thinking about her hormonal balance because that is something that can make women go crazy if they suddenly have a huge hormone drop/imbalance. I ask that because I experienced that myself and had to have hormone treatment.