If she is genuinely cold, after consulting with a vet, you might try a heating pad. We have one for our cat and he really enjoys it. they come in various sizes and most will automatically shut off after a time. The low setting is just barely warm, which should offer comfort to a guinea pig without overheating. Please let us know what the vet advises. If you can't get Piglet to a vet you might check on line. I didn't see much information on PetMD but thre are other sites. Good luck.