Agreed with the rest, but just to clarify - because I don't think she was really out of line:
1) They had a cabin, which is pricier than just a campsite
2) She was willing to pay the difference to stay at a different resort (just no availability)
3) I think she was just expressing her disappointment, she has come back several times and said to the effect of "hey we still are at Disney so yay".
Just don't want her lumped in with what are sure to be horror stories of really out of line crazy guests.
I think you put it well - yes people need some personal responsibility, but so does Disney have a responsibility as the owner of the resort - but in both cases, people who really do act crappy to others when everyone is in the same boat (CM or guest) are the ones that you want to put outside in the rain...