lucky power thief/ clueless villain

Mary was always a bit clueless at times, still she was generally fairly lucky with her favorite style of shirts. But when she finally got her grandfathers power for stealing peoples strength and boosting her own strength and endurance, she decided to go to the school for the empowered (well her parents decided after she showed everyone her power and putting several kids in the hospital due to sudden loss of muscle mass)

Scenerio
someone has talked the young girl into fighting the PC's and seeing if her power is really as good as she hopes.