She quits if something ISN'T easy, because well, she assumes "I am just not good at _____." It's maddening. But she also doesn't tolerate repetition or arbitrary demands to "demonstrate" long-since mastered skills, either, which makes for a fairly narrow band-pass filter of appropriate challenge.
I think this reaction is fairly common among gifted kids. It's natural to some degree, too. If everything has always been easy, a young person has no concept of the fact that sometimes it's necessary to think hard about something before you get it --- no matter how smart you are. And of course, if she's never had to think hard, doing so will be quite a challenge at first. Focusing on something hard is not easy. It's a learned skill.
This idea probably applies to anyone who could be described as gifted (e.g. in sports or music).
I've talked about this idea at length with my eldest (almost 11). I tell him that people who aren't gifted in school learn to "think hard" from an early age. I also give him parallels in other areas (e.g. "Remember you thought you'd never be able to do a mohawk on ice skates? You kept trying, and now you can do it, right? Well, <insert subject name> is the same. Just keep trying.").
