Why don't you rent/buy some DVD's for her?
The Book is a great collection by the guys from the Wakeboard Camp and it's great for every level of rider! It also includes cd's for the intermediate to advanced rider!
Also, crud, what is the name of it.....
UGH-another DVD that is good for skill...
Maybe it's Pre-Pop....I can't remember.
But I definitely would say get her a DVD to watch so you can slow it down and she can see what she needs to do. It sounds like she's trying and trying and just not there quite yet.
Remember to have her keep her eyes on the horizon, too. Don't stare at the wake and concentrate on that too hard. Tell her to casually go out and progress back in and just go through the wake, standing at the top and looking at the opposite side shoreline or something....
Good luck!