I think that you feel that neither of you will take things too far, and I am pleased to hear that you won't try anything like this on her, but just consider this ...
You are only 15 ~ what would you do, if your or her parents found out and became so upset and concerned that they stopped you seeing or contracting each other at all??
You don't see each other very often. You are under-age. You have never even kissed.
This isn't the way to start a relationship. Start slow.