When your boyfriend once had an affair

It's going to be interesting. Yes, I can say that with certainty. So, here's the deal. Over a year ago, before we met, my current boyfriend, got tangled up in an affair. A real, "she's married" kind of affair. And it's not a pretty story. She was miserable in her marriage, she found out she couldn't ever have kids, my boyfriend reminded her of the ex (from before her marriage) who she never quite forgot, etc. My boyfriend, on his part, had just found out that his ex (one mentioned in my earlier post) was dating a new guy. He, still being hung up on her back then (this is before we'd even met) was in a bad place. So, married lady makes move on distraught single guy, and poof! Affair begins...

And then gets weird. After spending clandestine time together twice, she confesses her love for him. He feels awkward. She then becomes obsessive. She starts to tell him that she's going to tell her husband who will more-than-likely kick his ass over it. He starts to feel panicky, but is also lonely and confused. Eventually, the pressure gets to him (about a month, month & a half in) and he breaks it off. Understandably, in my opinion.

Enter craziness. She calls, messages, emails, etc. And does so excessively. She is neurotic at this point. He cuts off all contact. This is new for him. He's had two relationships in his life before this little debacle and one was in his teens, the other was long term. He is unprepared for this. He feels guilty, but cannot handle the stress of being involved, and doesn't really want to be involved with her.

Cut to today. He has not seen her since he ended it. She has been in counseling and on meds. She has worked it out with her husband. He is over his ex and with me. And tonight, we're attending a party at his best friends' home and this woman will be there. 

Here's what I'm curious about. When my boyfriend and I met, he was so shy and timid. He was shaking all over when he wanted to kiss me the first time. He was certainly shy about having sex for the first time. I simply cannot picture the person that I know and adore being able to get involved in an affair. Really. He must have been so messed up about his ex, which is a weird thought for me. I know he's over her now. I just am interested to see what kind of woman seduced him. So odd to think about. I'm sure it will be a bit awkward. I'm sure it will not go as I imagine.