First time posting in AIBU, I really don't think I am but DH won't discuss it properly AT ALL
DH and I have been married for 6mo. I've known him 2 years. We're in our late 30s and met online. He was always open that he was looking for a serious relationship and our relationship is great. He can be a bit immature and there are things I'd like to change about him but overall I'm happy. He is in a very niche job working for the government that needs a lot of specific, high level qualifications (PhD as a minimum)- it can be very demanding and a lot of it he isn't allowed to talk about. (this is relevant!!)
He has this female "friend" who he met many years ago. She is in the same job but is 10 years younger and though he wasn't her manager he mentored her when she first started. They do seem to have a lot in common- DH has some quite strange interests that I think he's a bit old for TBH. They became friends and stayed in touch but there's always been something "off" about her. I've heard from friends who knew him before he met me that they used to go on "dates" e.g. for dinner or films even though she has a partner. That hasn't happened much recently. She's been with this partner a long time but they're not married so I'm dubious as to how serious she is about that.
Anyway I went through his FB messages and whatsapps and it seems like they message quite frequently- at least once every week. Sometimes she starts it, sometimes he does. Usually it's about some of these weird interests or sounding off about work- again the very specific stuff about their job that us "plebs" wouldn't understand - but I've noticed that she has a pet name for him that no one else uses and he uses a pet name for her. She sometimes ends her messages with xxx. They are due to be away for work in London in a couple of months. It's not required that they go as it's a seminar type thing, but I found a message from him asking if she was going and saying that he'd go if she does! She had replied saying thank god I'll have someone to sit next to, you're the only person I like out of all of them!!
She has in the past tagged him on facebook and it's always a bit inappropriate- like they both went to this comic book expo thing and she photographed him there with some models.
I have met her a few times and always felt she was actually a bit rude/cheeky to my DH- especially from someone so much younger who is in the same job and should be looking up to him. He says she's not rude it's just "we think the same way". I think she's a bit snooty as she seems to presume me and DH will have the same interests. We had her round for dinner once and it was awful! She's known DH's cat since it was a kitten so it loves her (cat hates me, I hate cats) and she made a bloody great fuss of it. She then wanted to talk politics which was a bit controversial as DH and I don't agree and she openly said she was shocked by that and not agreeing would be a "deal breaker" for her and her partner!
He wanted to invite her to our wedding but I said no. She sent us a card and a small gift anyway which I thought was quite passive aggressive!
I have tried to get him to talk about her but he just tells me to leave it and that there's nothing going on. I can't put my finger on it but it just doesn't seem right for him to have this sort of relationship. All his other female friends are our age, married and he's friendly with the husbands too. I've tried looking her up on facebook but her privacy settings are very strong so I can't even message her directly telling her to back off. I could get her number off DH phone but that seems a bit OTT
How can I get my DH to see this is a bit weird, and am I being unreasonable to think he should reduce his contact with her and keep it just professional? She's a young girl surely she should be making friends with people her own age anyway!