I've been there and many others here have as well. After my experience I have vowed never to let it happen again. What you need to do is take a step back, keep distance away from this girl. Focus on stuff you like to do, keep yourself busy with hobbies and friends. You need to understand that not everyone is meant to be. If you are getting no where with her then move on to someone who respects you enough to return kindness you give them. She may be a good friend but she is not helping you by keeping your heart dangling on a string.