Hello and welcome to YT
I'm sorry your little one isn't feeling well. Have you given any new treats lately? Some that are made in China (most brands of Chicken Jerky) are sickening and even killing some dogs.
Maybe she got ahold of something outside? Any different plants than the old house, mushrooms croppig up in the yard? Sago Palms are highly poisonous as well, so if you have any of those around and there's any way she could have eaten a seed, she needs help now. Regardless of what it might be, she needs to see a vet. It would just be helpful if you knew of anything to tell the vet so they have something to go on. These little ones don't have much reserves and they cannot go on and on without medical intervention. A dog that won't eat is a sure sign that something's wrong.
I hope she's better soon!