How do I make things right ? How do you perceive this situation?

I’ve been getting really close with one of my friends lately. I am bisexual so I’ve been calling her my girlfriend for some time and I’ve been having a girl crush on her for a few months and I say lil sexual shit here and there and we just laugh it off and not take it seriously . Last night she put her breast in my mouth and I started laughing (she was fully clothed) but something told me she was seriously... but I thought she would go that way cause she’s straight . I don’t want to scare her off or away from me or ruin our friendship but I do wanna tryna fee things with her but idk how to go about making things smoooth, right and comfortable for both of us.