My family and I are at WDW frequently, (at least once a week.) Over the years, I think we've seen just about everything. There are so many incidents where characters were out of character, CM's arguing with each other in front of guests, managers confronting subordinates in front of guests, etc. The incident that sticks in my head the most happened at POR food court. 3 CM were arguing over the "toothpicks" to put into a burger. The argument actually got pretty heated and lasted over 10 minutes til my husband cleared his throat and told them he didn't plan to eat the "toothpicks", but he'd really like the burger before it got cold.
With that being said, these negative experiences don't happen often. I think when they do happen, they stick in our head because they are so rare.
I've also noticed that the magic that is so common, becomes expected and we take it for granted. We've had so many magical moments that we find ourselves wanting more. For example, once we were asked if we wanted to ride Spaceship Earth. We said sure. The CM took us inside through a different entrance and put us right on without waiting in line! Another time, it was close to closing and ds and my niece and nephew wanted icecream. They arrived and were told the man in front of them was the last customer. The CM and his manager saw the disappointment on the kid's face. They did the sale, then walked up to the 3 kids and gave them Mickey bars! They were so happy!
Ok, enough babble. Here's my point. As for the doubts the OP has raised, yes, that would be very rare. However, once when I took ds(at the time 3 months) up to Winnie the Pooh, he kissed him and told him (yes in regular speech), "I love you." As we walked away DS(10years old) at the time. Said, "Mom, I thought Pooh wasn't allowed to speak." We chalked it up as another magical experience. How often do you get a non-speaking character to speak!? So to the OP, yes, I do see it possible for Aurora to be out of character. It's just sad it would be that much out of character.