"Can you explain what you need to do?"
Students are often still unclear about the requirements of a writing assignment, even if it was explained and discussed actively at school.
If you don't get a clear understanding of the task from your child's explanation, it's because she doesn't have a clear understanding. In this case, read the description of the assignment and explain your interpretation of it. This may elicit more information from her.
Come to an agreement about what you think is expected, and let her know that if there is a problem at school because you have misinterpreted some of the requirements, you will support her by talking with the teacher and explaining your discussion.