The first piece of information that dolly is grateful is that she repeats how much she likes her coats. That shows that she is grateful/loves what she has. And she is not jealous of what other people have. She doesn't complain about what she doesn't have either.
The second piece of information about dolly being grateful is she doesn't care of what it is made of. In the the story it says that she makes her coats out of the rages that they had left. Dolly doesn't complain about that. She