I really need help what do I do?

first of all your only 15 i know she may seem like the only girl you want right now, this will change since your so young. When i was 15 i was the same way, if you do end up dating her you will see what im talking about when you find another girl that will be better than her and then the next will come along believe me there are so many girls that you will come across and if this one doesnt want you so what, its not the end of the world and you will com across other girls throughout your whole life your only 15! and if she is the one things will happen for you guys, and if shes using she doesnt want to loose you as a friend excuse you need to really find out why shes saying that,, it could be her parents dont want her dating, could be she likes someone else. If you are serious about her you should tell her you want to try it out and promise her even if it doesnt we will be friends have it in writting or truley mean it to her so she knows. GOOD LUCK!