First of all, she may be uncoordinated in this exercise if it is new to her. That will change over a week or two if she continues to do them. She can start with the easier version with knees on the ground until the form is good, then when she gets the reps higher on those try the standard pushups and stick with them until coordination is no longer a problem.
Also ensure that her hands are about shoulder width, they don't have to be wider; typically she'll get more power with a shoulder width grip.
Womean have less relative upper body strength. Some of the things she can do to build strength for pushups are pushups with her weight on her knees, bench presses, dips, dips on a gravitron if regular dips are too hard, pushdowns, etc. until her reps go up and she's able to do regular pushups.
Standard pushups would be a good goal, or just stay with weights or pulleys-flys, benches, pec deck, cable flys/crossovers, etc.
