Im not gay but i still like girls

Alexandria
A lot of people i hang around are gay, lesbian... Anyways but i met this girl thats an amazing person. But also had a great sex appeal.  Sometimes i find myself not knowing the differene between liking somebody and just wanting to have sex. She seems somuch more mature than i am but i know sex is sex. How can i tell her without sounding vulgar that i just want to have sex with her. Im 19 shes 23... And shes gay also. Any tips on how to approach and if i get the chance what to do?