She needs to be able to connect the spin of the ball with her release/pitch. The spin has to be visible, so take a marker and put a large black dot in each 'horseshoe' of the ball or mark the seams (I prefer 50 cent piece size dots). Then have her pay attention to the spin as the ball crosses the plate. She should be able to figure it out. The most common fastball spin that I see is half bullet-half top.