I think they mean she favors riding her toe side edge over heel side edge. Thats the only thing I can think of. I know for myself riding toe side causes leg fatigue a lot faster. Heel side is more relaxing. So maybe thats what they are referring to. Her preferring and feeling more comfortable on her toe side than her heel side.
As for as which foot is first, their method of which foot you kick with is a bad one. A better method would be to have her take a short run and slide across the floor. The foot that naturally goes first is the way she should probably ride a board.