Bisexual virgin

I am attracted to girls and boys (but mostly girls). I have a high sac drive but not for boys and I am still in the closet. I am 17 and I am about to graduate high school and would love to get eaten out before I graduate. I am just too shy. Well I have a lesbian friend that has offered me an opportunity to get eaten out by her but I know her ex girlfriend (and lesbian relationships are most of the time complicated) even when they’re broken up and I don’t know if I should tell her I am desperate to be eaten out and I like her.

I really don’t know what to do. I need help ASAP.