Need help with this girl

[prepdj]

Last year at the beginning of the year this girl always stared at me. She was always looking at me. So one I walked up to her and we started talking and texting. She would wait for me outside my class and she made it seem like she wanted to be with me. So after two weeks I asked her to be my gf. I know that was a mistake but I still did it. She said she really liked me but she didn't want a boyfriend. After that I didn't talk to her the rest of the year. She stared at me everyday still though. So this year she doesn't look at me much. But she comes into my store where I work and is smiling and flirty with me. So we have small talk. So I decided to text her. She replied good but after 3 messages she said wait which "name" is this. I told her and she thought I was someone else. So I asked how her day was to change the subject and she didn't reply. Should I talk to her in person? Why would she do that? And it was only a 2 month summer break so why would she stop liking me that fast? And why'd she flirt with me. What should I do? Does she want me to chase her?