“Harry Potter” may have been her salvation. Although, it also seems obvious that she had decent parenting. For an entire decade, covering her teenage years, she had to walk the straight and narrow in order to preserve the brand and keep her job.
Seeing as how easy it was to replace the late Richard Harris with rotating Dumbledore’s it must have been made clear to our young stars that they too, could be dispensed with if they broke the unspoken covenant and turned into Hollywood brats.
Now they’re all thought of as “serious” actors and I’m sure they want to keep it that way.
Well, I wouldn't call it "rotating." After all, Michael Gambon was the only other Dumbeldore in the movies... Interestingly enough, while I loved Harris' portrayal of Dumbeldore, I think Gambon played him more energetically, and did a better job than Harris might have in the later movies. But Harris was perfect in the first 2 movies.
Mark