You cannot transfer the purchases to another account. What she has purchased with your account will always be tied to your ID. That's the way that it works. You can have her create her own Apple ID to use with Cloud account, FaceTime and Messages.
But if you create a new ID for her, she will have to flip flop between the two Apple ID's in order to update apps, and if she wants to make purchases with her own ID, you also have to consider the fact that she may run the risk of locking herself out of her own ID by downloading a past purchase using your ID, after she starts buying with her own ID.
Read this about associated devices in iTunes.