Is it normal that i still want to be with this girl?

I met this girl online this summer. She goes to my university. We began texting really frequently but we never got around to hanging out. I did run into her twice though. She began telling me about her insecurities. She said that guys have used her for sex, and have treated her badly. I did my best to make her feel better, and I told her I thought she was pretty. She said I was the nicest guy she knows. She said that not a lot of people care about her and it meant a lot that I care. I really thought we were connecting.

Then a few days had past without her responding back to me. When I got a hold of her, and asked her what was up, she nonchalantly said that she's become smitten with this guy, but was still willing to be friends with me. Now after knowing this guy for a week they're officially a couple. At first I refused calling her a hypocrite saying that she can't complain that guys treat her badly when she just ditches someone who was really nice to her right when something better comes along. I didn't even get a chance to go on a date with her. However, I later changed my mind and said that even though she mistreated me it doesn't make her a bad person. That was four days ago and I started with one conversation since then.

Her rejection was a week ago. I've barely spoken to her in real life. She's not even that pretty. Why do I care about her so much? I honestly don't think she's ever going to reach out to me again now that she has a boyfriend and sees no use for me. Is it normal that I still want to talk to her, and can't seem to just forget about it and move on.