Unless you’re Rapunzel, hair doesn’t grow this long
Brave’s Queen Elinor has gorgeous long hair that cascades down her back, past her knees, and all the way down to her ankles. It’s beautiful hair, but… how is it so long? While it’s possible for hair to grow a dozen feet or more, it’s pretty rare that such a thing would happen. According to HowStuffWorks, the average person’s hair won’t grow longer than about three feet, even if they never cut it.
It’s clear that Elinor isn’t actually wearing some sort of primitive hair extensions because, if she had been, they would have fallen out when she turned into a bear (and would have been gone when she later turned back into a human). Maybe long hair just runs in the family? Is it possible that Elinor is actually a distant relative of Rapunzel? It would certainly explain where Rapunzel got her long locks and would also be in keeping with Disney/Pixar’s love of including little nods to other Disney films in their movies.