18[m] This girl likes me 18[f] but the problem is, I like her best friend...18[f]

So I'm currently a freshman in college. A girl I know clearly likes me. However I am quite interested in her best friend. Should I try to make a move on her friend or would that seem to be a douchebag move? Also, do girls have a code in which there would be no way that they would like the same guy that their friend likes?