How bizarre. My wipers are stock EK wipers and Rain X is one of my favourite things in the world.. I guess it works differently with different wipers.

Anyway, if it's not working for her screen/wiper combo, two steps- she could try a bucket of hot soapy water for the screen, then after that cleaning the wiper blades with alcohol (like ethanol or similar). Or alternative to the alcohol is changing wiper blades.