I don't think you need an emergency vet appointment. Pudge is just stressed because there is a new cat in the house… that is all the vet will tell you… you don't need to waste big bucks to hear that. She is still eating. She will adjust in time.

I like Diandra's idea about the baby food!

Have you thought about switching Misu's to Pudge's food, too? At least on a trial basis? It seems like a hassle to buy two different kinds of cat food.