is she being shy or is she not interested?

There is this girl i like but things have gotten awkward. I met her in 9th grade. She used to show plenty of signs that she liked me for example,Looking and smiling at me all the time, Talking to me a lot, Sitting next to me when she usually sat alone, She offered me things, Its almost as if she was just making an excuse to talk to me. Then in tenth grade i told her i had feelings for her. The next day she Starts acting shy and kind of avoids me. She wouldn't talk to me unless i talked to her. She used to look into my eye for 2 seconds and smile and look down. i took this the wrong way and thought she wasn't interested and didn't talk to her for months. Afterwards i talk to her again and she told me she got back with her ex, who she is broken up with now. I wrote her a letter to her so she knows i still like her. This is where i am stuck at. She is still acting the same as she did before. She won't give me any eye contact and if she does its only for like 1 second. She avoids me, If i try to talk to her, she is listening but she is just not acting like her normal self (note she is usually very enthusiastic with everyone) She won't go out of her way to talk to me anymore and she talks with everyone else around me (mutual friends) I want to talk to her but i just keep saying to myself.. Should i even make the effort. A friend of mine asked her if she liked me and she apparently said no. I think she may be hiding her true feelings. She did just go through a break up after all.