For Part A, the theme emphasized by Meg's actions in Chapter 12 is:
People have the ability to solve their own problems once they stop blaming others.
This reflects Meg's growth and realization that she needs to take responsibility for her own actions and choices instead of placing blame elsewhere.
For Part B, the detail that best supports the answer to Part A is:
"I wanted you to do it all for me. I wanted everything to be easy and simple...So I tried to pretend it was all your fault...because I was scared, and I didn't want to have to do anything myself—"
This passage demonstrates Meg's acknowledgment of her tendency to shift blame and her growth in taking responsibility for herself and her actions.