Is this girl insane or what?

So I live very far away from home, about 2 weeks ago I went home for the first time in 2 years. Some girl that I've never met in my life added me on facebook and was talking to me the whole time and texting me nonstop. I was kinda stupid and agreed to go to the movies with her so now for some reason she think that I'm in love with her. Now that I'm back to where I live she keeps telling me to never leave her and that she doesn't know where she would be without me. I guess this would be acceptable behavior if it was from a girl I knew quite well, but I literally hung out with her once and never saw her again. I'm trying not to be a jerk and hurt her but how do I tell her that she's acting like a crazy person?