I'd suggest that you open up an account for her at Chesstempo.com. Have her do tactics and if you wish upgrade so she can do end game puzzles too.
What's nice about computer puzzles is that once you miss it, the program will show you the solution. She needs to figure out why the answer is what it is. If she doesn't understand, you need to be there to explain why the moves work as they do and why what she did was wrong.
I can figure out why I was wrong a vast majority of the time, but at times I either just lump it and go on or post a question on a chess forum.
Chess tactics puzzles will do a couple of things for her. Number one it will help to develop her board vision and number two it will show her how certain tactics work.
Both the tactics and end game puzzles are given ratings so she will always be working at her level, once she hits her rating.
I also like Chessvideos.tv, they have some puzzle generators for working certain situations. This is the one that I used for learning how to checkmate with queen vs knight: http://www.chessvideos.tv/endgame-training/king-and-knight-vs-king-and-queen.php