This question is a bit hard to answer because I'm not sure what "break" refers to. I assume, though, that it means some kind of "school break" or "holiday," like having Spring Break or just a few days off of school that's officially approved by the school district. So when the teacher said this, she was likely saying, "Your daughter really liked spending time with you during the break. She doesn't want to be at school because she wants to be with you! It's hard to go back to school not just for her, but for all of us." It's a bit of an odd expression, though, since I don't know why a break would be "hard" -- breaks are supposed to be relaxing! That's what makes me unsure if I'm correct or not.

The break is usually the time for food and rest in schools. If she was referring to that break, then it is possible that they all had difficult moments. It could be that a lot of children cried, perhaps some fought: things were not easy in general. And that it was not only your daughter that was affected.