My best friends make out with each other what do i do?!?

ok, this guy ive known for years he met my friend at a party and now shes all over him and flirting with him. i didnt really care until someone said she kissed him then i got this "why'd u kiss him attitude!!!?" shes still my friend but hes all she ever talks about and hes always around me so i never get to talk with just me and him.... the thing i dont get is aftr all these years ive nvr lookd at him anymore then a friend... so how am i getting this jealous attitude??? ive dreamed about him the past two nights and its getting awkward between me an my friend... wut should i do???