i think she may have stopped the relastionship, because at the moment you are fragile. You need to grow in confidence and discover for yourself who you are. Her being your first is a lot of pressure, and so maybe she didnt want you getting to attached, and coudlnt deal with it.
All i can say is only she knows and im surprised why she didnt explain to you why she wanted to continue with things. I wish i could give you a big hug, things will get better. Your emotions are raw and your in thick of it at the moment. You will pull through. Good luck xx