Yes, if you're a teacher, it makes your reaction to this even more un fathomable to me. Are you currently teaching?
In schools these days, there has been recognition that constant praise where it isn't warranted isn't helpful.....it becomes empty and doesn't achieve anything. This teacher does need to encourage her pupils and I am sure she does - from one comment,met here is no indication that she never says positives. However, she's looking to help her pupils improve, so constructive comments about how to do that, about all kinds of things, including who students work with are needed. They are intended to be constructive, not belittling.....there is a very real difference.
In schools today, children are always setting themselves targets, hearing about the good aspects of their work, but also 'even better if...' comments too. It can't all be 'wonderful, wonderful, wonderful' from school.....or you either! How can people grow if they have no sense that there are things to change, or to be able to hear them without a flood or tears.
Goodness, if this really really worried you, contact the teacher for clarification about what happened. However, I see no need and you making a mountain out of what isn't even a molehill. Your DD is going to face comments like this,mconstructive comments over and over again.....and some won't be as gentle as this one, and she and you will need to cope, if she's to grow up to be a sensible adult and not a wimpy princess Who can only ever hear praise. So, if you can summon the strength to do this now, I'd have a rethink, alter my tone with DD from 'fuming' to acknowledging her feelings but also to see the other side and to quickly move on. Often the job of parents is to help children understand constructive comments, see the matter from all sides and how to not dwell on very minor setbacks. Parents who do that,mice their children so much more, than if they fume, disable their children from seeing all sides or from moving forward.