Wow! I feel bad, cuz all my friends are fine with me being bi.I suggest you talk to her, and ask her why she doesn't support LGBTQ+ (or lesbians, kinda same thing).If she does not support after that, tell her that you are lesbian, and you were born that way.Tell her you can't change, and you are proud.If she doesn't want to be your friend anymore, whatever, she's not a goof BFF if she leaves you.
P.S.if she pretends to accept, tell her you want her to be truthful with you, and get it over with.
-bi people exist