sounds like she is comfortable with telling you intimate stuff, ask her if she wants to see how you stimulate yourself, maybe you can pick up some tips from her that way it is known that she has to do it to.
ok if she is your bestfriend. i dont recomend doing anything with her, the feelings will pass. and its not worth risking a friendship.
if you want her plan carefully. tell her you entertain yourself sometimes to the thought of sex with a woman, if she asks who tell her its her and if she responds angrily, say your just kidding its jennifer aniston or someone then you know its not gonna happen and the friendship is still good. you could just ask her has she ever experimented.