I'm glad the meeting went well. It reminded me (a little) of one of my husband's relationships. He's away for 7 months and is now somewhat close (within 4 hours) of an old girlfriend from many many moons ago. They got to talking a while back and now that he's been closer, they've met up twice. He told her all about me, but she's truly monogamous and doesn't seem to want to consider me at all.
Hubs and I have talked about it. After the last time she visited, he thought that it had been nice to catch up, but it definitely wasn't going to last. They may get together again before he comes home, we'll see. I'm okay with that as a temporary thing, old loves and all of that, because of the type of relationship it is. If it was more often, if it was more deeply felt, I'd definitely have an issue with it. I don't need to like the person he's with, but I do need to be acknowledged as being a part of his life.
I also worry that she's going to get hurt, even though he's been clear with her from the beginning, because she seems really monogamous and I think the idea of multiple relationships is so foreign to her that she has it deep in her mind that he must be unhappy in some way or he wouldn't see her. But that might be just my brain making that up.
I like the "paying the emotional tab" part, too. I agree. It either hits in the beginning, or later when they realize that it things aren't going to change in the way they thought.