I (15M) just found out my gf (15F) is bisexual

I recently found out my GF is bisexual through a very trusted friend of mine (This friend is certainly not the jealous type, nor do they have any interest in me).

As a Christian, this news really shook me, as we are taught not to practice homosexuality. As far as I know, she has never had a homosexual relationship. I've prayed and read scripture, and as far as I can understand, homosexual attraction is not a sin, but acting on those emotions is a sin.

Her friend said my GF planned on never telling me, but I don't know if I could continue this relationship knowing she's not being fully honest with me. So far, this has not changed how I feel about her. I still love her to death but am conflicted about what I should do next.