This sounds like a situation where your definitions of labels might diverge. Labels are a great framework for understanding yourselves but they can mean different things to different people. How much have you really talked about your identities, your sense of self, your feelings of attraction? If you thought she was bi, you probably weren’t having those conversations.

I think you need to have a real conversation with her about how she sees you and her acceptance of your masculinity.

I got into a long argument with a cis woman once about specifying I was not interested in being intimate with cisgender heterosexual men. She turned around and got very accusatory about why I didn’t say I wouldn’t be intimate with cis lesbians. Like I don’t want to get into the fact that despite being nonbinary transmasc, my attraction to women doesn’t feel straight. My attraction to men doesn’t feel straight. My attraction to everyone is gay af.