I would worry more about her denting the box than her Frederick's of Hollywood heels make holes except that I don't think she weighs enough to actually make a dent.
We have Rock Band and Beatles Rock Band (or I should say my daughter does). Although I like the simulated drum and am always happy to provide the vocals, the guitar and bass are just silly. It doesn't simulate guitar playing at all. To me, it's just another big video game controller (to which I will admit to being totally video game challenged). I will say though, that when the kids don't take it too seriously, we have a lot of fun because everyone in the family can join in.