Here's a link about negative growth on the NWEA MAP. I would go over this with her and see if any of the reasons ring true with her. This part sounds the most likely:
Quote
Some students may "cherry pick" items on the test. That is, they will correctly answer items that are easy enough to solve quickly and guess on items that would take more work. This can lead to deflated scores.
http://www.nwea.org/support/article/554/negative-growth