I think that sometimes teachers think you take a class from them because you want to be as good as they are, so they think it's constructive to point out the mistakes you make. She might think you want her to do that too, because you want it to be as "perfect" as possible, or you want to know when you are making a mistake, even if that mistake doesn't really affect the projects outcome.
If you like her, then listen and then continue merrily on your way. I teach and my motto is that the mistakes we make are what make our projects uniquely our own. And sometimes mistakes turn out better and a new technique is born!