If she's not used to being dressed or just doesn't want to be dressed today, she could be in the "give up" mode, as some of them do when dressed against their will. Or she could be feeling bad, coming down with something. Could have been scared or worried about something going on in the house; with the family, other pets in the house, if any; heard a strange sound she's worried about - something like that. Why don't you try undressing her and see if that perks her up. If not, just keep an eye on her and watch for further symptoms, etc., get her into the vet if anything worrisome develops. Hope it's nothing - just a spot of rebellion or her having a funky day.
__________________  Jeanie and Tibbe One must do the best one can. You may get some marks for a very imperfect answer: you will certainly get none for leaving the question alone. C. S. Lewis |