XRs,
Have her hold the clutch in, and roll the throttle on very slightly, and keep it there so she can feel the revs of the bike. Then, have her slowly let out the clutch until she can feel where it starts to pull the bike. Pull the clutch back in, then do it over and over again so she gets used to finding the disengaging point on the clutch. When she's comfortable with that, have her let the clutch out slowly to the disengaging point, and roll on a bit more throttle to get the bike moving, and then let the clutch out all the way. I think the issue is that she needs to understand that the clucth is not an "on-off" switch, that there needs to be a smooth transition to keep from stalling the bike.