It seems that when she trys to go the the toeside her weight isn't shifting or rolling to over her toeside. You can also tell that when starts to try to do an s-turn her weight is a little more on the back foot then the front.
Suggestions to work on the the first part. See if she is able to bend her boots at all by her trying to squish it in half. For example, put your fingers between her chin and tongue and see if she is able to pinch them. Make sure she doesn't bend at the waist with her butt sticking out when she tries this. If she can then she should be to use ankle bend to help with her toeside making this movement. Typically this movement is called "squishing the bug" and it is typical of knee bend and ankle flex. Otherwise a bigger movement about hip level (leaning up the hill, once she can "feel" or understand where her weight needs to be she can start moving away from a full body lean) can help if the boots are too stiff.
Also to start off with her toeside have her try a j- turn in this sequence. Start with her at a stop with board pointed down into the fall line.
1. get up to a flat board and start sliding straight down.
2. squish the bug and lift heels slightly, think of looking at a 45 degree or diagonal down the hill
3. Rotate shoulder hip and knee(think knee over pinky toe moving acorss the foot to the big toe, knee is flezed over the toes) across the hill toward the side of the run to slightly up it. Eyes should have a reference point.
P.S. to assist you can ride slightly in front of her and have her follow your path.
This sequence might help her also get on the front foot too, might not too. Other exercises you can work on, nose and tail stands (moving toward nose and tail of board) flat terrain and then manuals on slight inclined terrain, focus on moving whole body over nose and tail and then on sliding nose and tail under her; flat land 360's (edge awareness) rotating full body, looking, and then rolling from toe to heel for wieght transfer; or put her in another lesson for more specialized assitance.
Hope this helps and that she has an awesome time sliding.