In our case, we know she is sensitive, but it's very hard to predict what will set her off. Charlotte dying in Charlotte's Web = fine. The Ingalls family leaving their house in the big woods and moving on to a new adventure = gallons of tears.

DD is somewhat infamous for being the 5yo who became completely hysterical when read The Giving Tree at preschool. (I hate that book.) To this day, she doesn't like to even SEE the cover.