My best friend is a lesbian and I'm not share if she's flirting with me?

I'm straight I resently broke up with my boyfriend and my best friend jokingly says will now we can be together I have no idea if she joking or if she's serious I've been looking up girl on girl porn and it really turns me on I'm not sure if I should tell her I want to be friends with benifits  because I don't want to destroy our friendship. And she knows I only was with guys so I don't want her to feel like I'm using her for the lesbain experience. What should I do? I don't want her to be my girlfriend I just want to do it with a girl?