Didn't Belle have curly hair? My mom always says my hair looks kind of like hers (my hair is more curly, though).
I'll be honest. The first time I watched The Princess Diaries, I didn't really think about the hair change! And Mia wasn't happy with it at first, because she had the hat and everything, right? And then in the second one, they curled her hair sometimes (but then, of course, they decided they hated the style....) Anne Hathaway has naturally straight hair. I don't get why they had to curl it (or give her a wig) in the first place, though. But that's why they kept it straight, and it didn't curl in the rain. It did kind of set a bad example for new and young curlies.
Aurora/Briar Rose/Sleeping Beauty (I still have trouble with her actual identity a little. Haven't seen the movie in years) had kind of wavy 2a hair.
As for the drawing, yes it is easier to do straight hair, at least when you need to see from a sides and back and whatnot. Curly hair is, at times, if not always, more complex than straight hair. It's the same with drawing it. Now, if you're just sketching, it doesn't really matter. I draw both types of hair.
I do wish more shows had curly girls, though.