/soy/ - Soyjaks

I genuinely can’t tell if I’m being reasonable or just insecure.
My boyfriend and I have only been together a few months. While he teaching abroad, he became friends with a girl over there. According to him, she was one of the only people around his age, and they ended up spending a lot of time together.
What started bothering me was that on days they hung out, I’d sometimes barely hear from him for hours, and then he’d call me for like 10–15 minutes at the end of the day. One night he called and spent most of the call talking about her and everything they did together, and didn’t really ask me about my day at all. One time he talked about how stressed she was about something and didn’t even ask how my day was.
He also put a few pictures of just her in the shared album from his trip, including Live Photos of her squealing over him smiling & posing for a picture saying “AWWWWW”. None of that proves anything happened, but it definitely made me feel weird. And she has a boyfriend herself but they are long-distance.
Now that he’s back home, he wants to go get dinner and drinks with her one-on-one. He told me about it himself, so it’s not like he was trying to hide it.
I don’t think men and women can’t be friends. That’s not my issue. My issue is that this is someone he spent a lot of personal time with, I still haven’t met her, and now she’s proposing they go out to dinner and drinks alone.
I realized I’d honestly be a lot more comfortable if I met her first or if we all hung out together before they started doing one-on-one dinners.
Would that be a reasonable boundary, or am I being controlling/insecure? Am I wrong to feel a little weird about this? He says this girl knows about me but around the same time that he was cagey about telling others on the trip that he had a girlfriend. I just get this feeling that he wants to appear single. There was another instance on the same trip where a student he taught was flirting with him, invited him out, and he didn’t outright reject her. Later when he told me about it he used unnecessary adjectives like she’s a blonde popular sorority girl. This is another girl than the other one fyi.
I’m genuinely asking because I can’t tell if this is something I should work on myself or if it’s a fair thing to ask for.