I was in a very similar situation with my husband when an old female friend of his wanted to rekindle their friendship. It was making me feel insecure and ugly (as a person). After a couple of months of feeling the way you do now, it hit me. I decided the best course of action was to just love him, not secretly consider the horrible things my mind was producing.

Our situation was different in that this woman has some emotional and anxiety issues and wanted nothing to do with me. But once I relaxed and focused on making sure he felt loved by me, everything fell into place.

I assumed I'd have to deal with this woman for a year or 2 before her issues pushed to the front and things between them would sour. Things took a fast track to crazy-town, however, and within another month she let the crazy out and my husband was not having any of it.

The fact that you have the option to get to know her is great. A bit awkward because of his spilling the beans, so to speak, but it's not like either one of them are excluding you. I say take advantage of that and start including yourself from time to time. You may gain another friend!!