That's a very bad thing, sometimes it's best to stay friends for plenty reasons. Because you may have feeling for her that she doesn't & you might open up and tell her about it and she will turn you down.. she will say:"no" and you will be hurt. And she might get with another guy and you will be very jealous and kick your self in the leg for never telling her.
Jealousy can over-rule any type of relationship... jealousy is a very evil thing.