Me and my best friend like the same guy..?

Ok so my friend lets call her (Jess) is like in love with this guy..lets call him (e.t) but he dosen't like her back, a while ago, iw as in town with my besties and he was there,he asked me to go out with him! but i did not like him at the time,well i sorta did.And i had to say no because i could not do this to Jess, after that day me and Jess never really talk anymore,today on the bus home,she asked if i liked e.t i said 'no' but she said its ok,and that i can go out with him or whatever she said she dosen't mind,but i know its actually killing her inside! i can see it in her eyes.The reason im worried is because i wanna go out with that guy! but my other bestie liked the same guy as she did before and they got in a really bad fight and Jess ended up not talking to her and now she hates her! i dont want that to happen between me and Jess! what should i do? and also only 2 people know i like him! my bestest friend and my other good friend! and im pretty sure my bestest bestie will tell her because theyre really close! what should i do ?