I think you might be right re the "senioritis" type feeling. Maybe have a chat with her about how she is feeling, what she is doing next, any items on her "wishlist" of things to do before she leaves your family. I would acknowledge that she is probably moving on in her head, but tell her how important it is to the kids to have her attention during the next couple months. Made it about the kids, not the laundry.
Also, I chuckled a little at the "WANTS to take care of kids" comment - sounds like she was a good interview! All APs say this (as did the Nanny I hired when DS was a baby) but everyone gets burned out/tired of kids sometimes - I know I do - so be sure to have a realistic set of expections for the next one