AITJ for getting pissed after I found out my gf was telling her friends about our sex life?

So I’m (22M) dating this girl who’s absolute goals in the gym-she’s got crazy muscle definition, especially her arms. I eventually got honest with her and told her her triceps are a massive turn-on for me. We ended up getting into this thing where I basically finish on her arms while shes just chilling there. It was hot and I thought we were on the same page.

Well, turns out she blabbed the whole thing to her friend group. Now they’re all clowning me and calling me a "creep" and a "weirdo" and the worst part is she was right there laughing along with them.

When I confronted her about why she’d share something that personal without asking me, she hit me with the "its my sex life too" line and basically said I’m naive for thinking anything in a relationship stays 100% private. She even told me I should just "own it" because it was my idea in the first place.

I feel like my trust is totally trashed. I opened up about a specific kink and she turned it into a punchline for her friends.

AITJ for making a big deal out of this?