are jealous or feel threatened in some way that their former husband is able to look better than they do?
No, I think they view it much closer to several other things:
1.) You're having an affair with another women, even if that other woman is yourself
2.) At it's very core, everything she believed about you, and about your relationship was a lie
3.) Whatever dreams, hopes, and aspirations she held and was working toward about the future are total junk.
All that coming together over the same information is shattering.