I tend to think thought experiments like if someone you love suddenly was the opposite gender is not useful, because it builds into the context that you already love the person. I just also don't know if that's how sexuality works - continuing to love your partner is not the same as continuing to feel sexually attracted to them the way you were before. The question is whether you think you have the capacity to feel attraction to women. It doesn't have to be the same intensity with which you feel attraction to men, and even the way the attraction works can be a bit different - but there is a question of whether you feel that attraction.

It's hard to know for sure. I struggled with my own sexuality and didn't realize I was bi until I was a teenager, but it was theoretical. I transitioned as an adult and my sexuality became much more balanced once my sex hormones were finally corrected - now I have experiences all the time where I see attractive men or women and feel obvious or overt attraction, where before I primarily only felt attraction one direction and I didn't typically feel overt attraction the other way.