Ooh, surprise requests are the best, sheila!
Actually, there's not much of an order except for the holiday books (I have several books planned or semi-planned), but the first one is where she finds Trouble (teehee). That seemed too overwhelming for NaNo, so I started with (because we just had Halloween) Halloween Trouble, which sucked, and then Trouble with Pets, which was my best planned one. And then I let myself lose NaNo for the first time ever so that I could focus on other projects, so I never got around to the rest.
TwP could totally be book 2, though. Oh, wait, no, Trouble in the Family has to be book 2 because her dad needs to find out about Trouble before anything else happens (though depending on if I flounder in this book, I might just combine the two). Trouble at School and Trouble at the Zoo are the other books that have been at least semi-planned, but it's sooooo easy to come up with themes for Trouble to mess up.