One of the things I've noticed about GT adults is that they (being perfectionists) tend to notice the things that they did wrong in a given project. So when someone compliments them, it embarrasses them and they feel it's necessary to point out all the mistakes they made.
I wouldn't encourage your DD to deprecate her work. I would encourage her to say, "Thank you" perhaps followed by "I worked hard on it" or "I spent a lot of time doing X." This way she's taking ownership of it; acknowledging that it didn't come exactly easy (even if it was easier than many people would find it); and (hopefully) she's setting up the internal idea that work/challenge is important.
