My DH met a woman years ago before he knew me, and they hooked up a few times. She was very keen on a relationship with him but he wasn’t keen so they ended up being friends and she married someone else.
She never really had a lot in common with my DH but they work in the same industry so they know a group of the same people. Over the years she has remained in touch with him in a low key way, always small messages, hellos etc. Nothing suggestive of anything other than friendship. But DH isn’t really interested and sometimes doesn’t respond for a long time, but it goes on and on. It has now been decades and this woman is still low key around. AIBU in thinking this is a bit odd? She still messages and tries to maintain relevance, asking about things he’s interested in, hobbies etc. Why bother? She has her own husband, children and life, my DH largely ignores her.