First of all, I'm sorry you heard this information about your t. It really puts you in a difficult situation.

Having been on the end of untrue gossip, and having seen the devastation that is caused when "half-true/half invented" stories go around, I would not simply take what the neighbor said as gospel, even if you think she is trustworthy.

For example, how did she know for a fact that your t had an affair? Did she witness the "act"? NO. So how would she know for sure? She may have taken her own observations about your t and her h, and then filled the story in with her own assumptions.

If it was me that came across this information, I would not believe it automatically. Some of what the neighbor said may be true; some may not. It doesn't mean that your neighbor is lying on purpose. She may believe what she told you - but she doesn't have the whole story. She can't.

I think it's vital that you tell your t what you heard - and the two of you work through this. I don't think you should just quit going to t.