Answer:
The paragraphs all provide at least one reason that Marcie seems unready for parenthood. Your teacher is having you pick these out and write a letter based on them.
For example, Marcie states that having a baby could help her grow up. She says this because her parents told her so. The fact that Marcie is listening to her parents about having a baby instead of making the decision herself is a reason why she might not be ready for kids. Try framing the letter around these points.