advice on how to start this conversation with my gf.

Hey, I’d like a bit of advice on how to talk to my girlfriend about the following. Sometimes when she sees men on TikTok or in a movie, she often says things like “smash” or “mmm what a hottie.” Usually, I just let it slide, but tonight while we were watching TikTok she suddenly said, “mmm what a smash, I wanna eat his dick.” I honestly didn’t know how to react, so I just let it pass again. But it really hurt me, and it makes me feel like if the right guy came along who was more attractive, she would just take him as her new boyfriend. Even if she means it as a joke when she says things like that, it really doesn’t feel good to me. Am I really so wrong for thinking this way?