I think she's just looking for attention. Maybe she just wants a reaction from you.
Do you not show your feelings for her to her? That could be a reason to act out the way she is.
It's definitely immature though, and she should stop. But I do need to know if you are one to keep your feelings bottled up inside cuz I dont think much girls like that. Now I'm not telling you that you should speak every detail, but some girls like when a guy is open with their feelings about them, or even given a casual compliment.
..::.*Love is giving someone the ability to break your heart but trusting them not to*.::..