Watching good players can give you/her some helpful hints. Have her watch some pro events on tv or live. Also, a very easy, inexpensive way of improving that is soooooooooo underrated is.......have her hit off a wall. I still do it when I get in a funk and it always helps me to work my way out of it. It is obviously inexpensive, as in NO cost, and you can really find a groove on your strokes, especially groundstrokes.