I really like this girl, she is straight but i am bi... she has invited me over, alone... HELP!?

i am a bisexual girl, and i am sooo in love with my straight best friend.. she has invited me over to her house, alone. you may be thinking... so whats the problem? but there is. I know we can't go out or anything stupid like that, but every time i see her, i just think of snogging her, and i am quite flirty with her, but i am worried that i am freaking her out. How can i control my strong emotions for her at her house.. alone!? any tips?