I’m bi but with a strong preference for girls?

I came out almost a year ago as bisexual to my mom, and apparently she told my step dad and my cousin (who’s more like a sister to me), but I wasn’t aware. My mom isn’t overly accepting of it but my cousin is, even though I just found out that she knew today. I’m extremely stressed about that but also i want to talk to her about how I mostly prefer girls and I want to fully come out to her and clarify some things that my mom may have said that aren’t true. Any suggestions?