AP's normally bottom out around month 6 or 7. First 2 months getting used to everything, hit their prime around month 3-6, then hit a slump of sorts where they either focus on their social life, annoyed with our kids, or both. They start counting down around month 8 or 9 to going home, so traveling in the US, or locking in a guy (as in they focus on "where is this going?" if they are dating an American). By month 9 or 10 they regain focus and want to wrap up on a good note.
You have an odd AP that must have something else going on. I would just ask her and be prepared to send her packing. 13:55 needs to review about 1000 posts about this on aupairmom.com - there is a pattern and you are not dealing with a slide.