I agree, that looks like a promising character.

My thoughts would be that she wouldn't know what was going on or what to expect. It would seem like a normal massacre situation. Strange as that sounds lol.

 The physical changes would come first, getting stronger and faster in larger leaps until he's topped out. Than the energy would start to come into play. He would start out resistent to damage and only slightly stronger than men. His muscles and skeleton are built tougher than average. So it's possible she misreads him and doesn't hit hard enough at first? 

 Before taking the evil turn Xavier was actually a battle hungry white Knight so I can understand that. I like the idea of her being able to come back to life if she's taken off guard or something.