sex with my close friend (complicated af)

so my friend who i go to college with has asked me over to her her house just for casual sex. right now im feeling really shaken and anxious whether to do it. yes, im a teenage boy and am 'ready', but all i am thinking right now is ways to get out of it while remaining her friend.
some history- she has a reputation of being a person who has a lot of casual sex and has many exs. pretty sure she is sti free. on the pill. we had a small drunken experience during last summer which ended up as an embarrasing joke(not going into this). and also, my male best friend has been in a wierd sex-ish friend relationship with her for like 6 months and this is like pressure as we both like the same girl and get jealous of each other which only ****s our friendship up. help and advice plz...