Been with my gf 4 years. 1 year into the relationship, she told she was bi. Back then I didn't give a shit because things were very rocky and I thought we didn't have a future, I just wanted to keep smashing. I did ask her why she thought she was bi, and she told me she had had strong feelings for a friend before. I didn't think too much of it and thought she might not even be bi and it was just a harmless crush. It was a literal 5 minute conversation.

Fast forward couple weeks ago, subject comes up again and she basically confirms she is as a matter of fact bi. Even though she's never done anything with a girl, she actually wanted to date and sleep with the girl I mentioned previously. It was also not the first girl.

Whenever I think about it, I am overcome with anger. I don't even know why. The thought of her wanting to have sex with a girl disgusts me. I also feel emasculated for her finding girls attractive. That's supposed to be my role. I never considered myself a homophobe, so I can't even understand why I am having such a strong reaction to this. I can't explain why I feel so angry.

Is it ridiculous that I am considering breaking up with her? She is otherwise a good girlfriend.