I cant imagine any design of rack that would fit that bike. If her bike is taller than the one in the picture you might be able to find/modify a rack to attatch to the seat binder(the clamp that holds the seat post in place) but on the one in the picture it appears the seat binder is lower than the max height of the rear wheel.


They are harder to get used to, and can be tricky to balance, but you might just have to go with a front rack.