Howcthappen, I'm glad you started this topic because I had similar thoughts and feelings. I absolutely hated the idea that she might think he loves her, he doesn’t really love me, he’s staying with me for the wrong reasons, etc. It’s good to know I’m not a weirdo for feeling like that!
Short story: few weeks before DDay he told her he’s unhappy in our relationship, he feels stuck, and that the relationship is not progressing. After DDay, I asked him (as part of the "no contact" conversation, which was technically "only strictly work-related contact", since he still had to work with her in the following months) to make it clear to her that she doesn’t mean anything to him, and that he loves me. He, ofc, didn’t do that – he said something like that he’s sorry for the way things turned out, and that he needs to fix things with me. On top of that, 2 months after DDay they exchanged a few inappropriate e-mails (he initiated it), which might’ve given her the impression that he doesn’t really care about me. Not to mention all the stuff he did during the betrayal, which might’ve given her the impression that he cares about her.
I was furious that she didn’t get the clear message: I don’t give a shit about you, I absolutely love my girlfriend (we got married few years later). I was told all the usual stuff: why do you care what she (or anyone else) thinks, you can’t control what someone will think, she got the message in the end (5-6 months after DDay ALL contact stopped since we moved, and he was no longer working there), blah, blah, blah. On a rational level, I knew all of that. However, my emotions about it were so strong, that no amount of rationality calmed them. And we weren’t even married back then, there were no kids, or anything that would indicate to her he’s staying out of obligation (except the fact that we were 11 years together, so there was some obligation present, but not as serious as marriage, kids, family).
For a very long time, I struggled with these feelings, I tried to convince myself I shouldn’t feel like that, I did my best to listen to others and convince myself it is not important what she thinks. One day I had enough. My feelings are valid, and no one gets to say what I should or shouldn’t feel. My feelings might be irrational, but I feel them. I don’t need to justify my feelings about this, or somehow make them rational, to be taken seriously. I feel them and I refuse to "live with them". I decided to do something about it.
I talked about it with my husband many times, and we made a plan. Perhaps she didn’t get the clear message early, but she can get it now! Ofc, contacting her years after DDay was out of the question. However, there are other ways. For example, he still had some contact with other ex-coworkers. We made it a point that he will find a way to mention me in any potential communication ("Hey, how are you, what’s up?" "Hey, I’m great, never been happier! Job is great, marriage is awesome, wife beautiful as always", and similar). There is one ex-coworker that’s very close to the OW – I’m pretty sure she saw the messages we sent to him. Also, if you have social media – use them to your advantage. We don’t have social media, but we do use one platform she uses too, and it’s possible she saw a beautiful-but-not-cringey post my husband wrote about me on that platform (I helped writing it). I also have a plan of what will we tell her if fate puts her on our path again (and with my luck, that’s inevitable). Oh, and I’m 99% sure she saw awesome photos from our wedding and heard how lovely and in-love we looked, but I won’t write details about it, that is, why am I so sure.
Howcthappen, your feelings are valid. Please, talk about them with your husband. Be a team – make a plan together how will you deal with those feelings. Perhaps you can do something about it, perhaps there’s a way to indirectly let her know now that he stayed because he loves you.
I can tell you – after what we did, I am aware she still might have some sick, twisted interpretation in her limited mind, but I am calm(er). As I know the message was sent and seen. This is the crux – not what she believes, but what my husband demonstrated. And what he will keep demonstrating, if an opportunity arises.