This is just my opinion, and it might be a little overprotective because of the loss of my Starr, but I'd take her to the vet before you go to California. Number one, to ease your mind, and number two, to really make sure that she's okay.
You're not leaving until Friday, so just try giving her HALF of the treats she used to get, you know a happy medium, and see if the weight starts coming back. If she starts to plump up in the next two days, she's more than likely fine and that was just too much of a reduction in treats.
Tracy and Luna