1) Count me suprised. I heard an interview with her a while back and she seemed (at least at that time) like a well spoken, articulate, politle young woman.
2) Who cares what Disney (or for that matter any other venue says) The venue makes rules and the performer makes rules (in thier rider) As a professional, if you agree to those rules, then you abide by them. If Disney has a "no cursing" rule (I assume a list is provided, and F___ is pretty much near or at the top of most lists) then you abide by the rule or you don't agree to play there.
3) I can understand a single slip. Cursing is commonplace - it's also lazy and uninventive, but that is beside the point. I should hope a person can controll themselves. If she was invited to play for the President (whomever he or she may be) would she respond "F-ing A man, I'll play that S___" or perhaps she would choose better words. People need to learn to turn on the filter between mouth and brain - not just with cursing, but with saying anything in general without thinking.
-dave