So my (f2m) son came out as bi, in middle school to me after I said a random comment about not wanting to donate bottles and cans to the local Methodist church because they discriminate against my friends who are gay.

I think was telling him how some guy came to our house looking for bottles and cans for the church, and I layed into him. It was several years ago when the Methodist church had just announced how anti gay they were. And a local minister lost his job because he preformed a marriage for his daughter and her wife. Maybe say some random pro-gay comments around her. But don't pressure her. Just let her know in your own way, that you are open minded. She will come out when shes ready. I'm still waiting for my nephew to come out.