Need relationship help please?

Okay so I am 17 and she is 16, I was her first boyfriend, first kiss etc. and she was my first real relationship. About a month ago I broke up with her after going out for over a year. There were a lot of reasons for the breakup, it wasn't anything sudden. I expected it to be hard and the first few weeks were but then I seemed to be getting over her but lately I cant stop thinking about her and dreaming about her and I will try to text her for any reason I can think of (like good luck on a test of good luck at her game) but she usually responds kind of arrogantly, like "ummmm thanks?". Her friends tell me they dont think she is happy without me but the way she treats me and the fact that she has never once initiated a conversation with me leads me to believe that she is completely over me. Also I know she likes another guy already and that kind of bothers me. Part of my knows that trying to go back out with her will be a failure either way, either she will go back out with m but nothing will change, or she will simply say no. But part of me wants her back so bad and is willing to make sacrifices I thought I would never make to accommodate her. If you have any advice on any aspect of my dilemma I would greatly appreciate it