Two ways to look at it. Either she really was joking, and doesn't think it's appropriate now that you're dating. Or, she thought you were a lesbian, but now that you're dating a guy, she realized that you weren't interested.
Are you sure your not into girls or at least this one? It sounds to me that your in the middle of a sexual identity crisis. Your too young to know for sure anyways. Just a little off track but she may not see you after school cause she is having trouble admitting that she likes you this way. :)
Hahahah wow! Teenage loving!
Pardon for the early chuckles.
Can you give more information on ways she shows affection on you? Because the ones you have just shared for my opinion are sexual acts, which I find normal even with straight girls doing it with each other because I have said it's a "sexual act" its a primitive gesture. Give me more like, does she laugh when she sees your messy hair but then pats you on the back or touches your head? something like that ... :D