it depends on whether the guy and girl find one another attractive. if so, then friendship alone cannot last. all TV shows with a male and female lead characters have some sort of sexual tension. the only exception is will and grace, where Will is gay. gracie finds will extremely attractive, but alas the attraction is not reciprocal. so yes, a girl and a guy can be friends if 1) one friend is gay 2) one is unattractive.