Why is my female friend avoiding me?

I have been friends with this girl for about two years. We have always gotten along great, we hang out after work, and we tell each other everything. I developed feelings for her about two weeks after meeting her, but I figured she would never date me so I decided to be her best friend instead. About two months ago, she comes up to me to talk about her dbag boyfriend again. I had tried being nice about the whole situation, but this time he crossed the line and I told her she should break up with him. She did it then next day, and was really happy after that. Recently however, she seems to be avoiding me. The last few times we were going to hang out, she either canceled or said she was busy. When we talk at work, she seems like she's forcing herself to talk to me, and she doesn't come to me for stuff anymore. One of our friends thinks that she has feelings for me, but she's so shy she can't tell me. I want a few more opinions before I ask her about it, since I miss having her as a friend.
Why is my female friend avoiding me?
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