If she's saying she likes you, then another day she says she doesn't, that means she's unsure of herself.
Try spending more time with her and doing activities with her. This way, you'll know for sure because she'll have fun with you and flirt with you and things of that nature if she likes you, or if she doesn't and is bored around you and you two aren't laughing and flirting and such, then she doesn't yet and you should find someone else or keep trying harder.
You can either try to get to know each other more so she'll like you more if she already does, or you can just find someone else. *Hint Hint* Try the first one!!! :D