I need some advice with this relationship?

Hey! You should move on and find someone else. Why would anyone deliberately ask you to have to try harder and harder? It sounds to me like she has confidence issues. What's worse is that she might be trying to use you for confidence building reasons (not the most likely scenario, but I've heard it before). Anyways, no use in pondering over something that's just going to waste time and effort. You're a high school sopre. PLenty of time to move on.