Why do I let her have control

Why do I let one person have so much control over my emotions. She used to tell me I can't base my happiness on her...and I would tell her that I don't. But you know what...maybe I am doing that. I missed her all summer. I was anxious and excited for school to start so I could see her again. And guess what? She hasn't given me one ounce of her time. I feel like I mean nothing to her...and that really hurts.