Since your dog is also not eating, it is very important you get her to a vet. Chihuahuas are so little that two days without food is going to be very hard on her body. The fact that she squeals when you pick her up indicates to me that she is reacting due to pain. Even if you're gentle, she's still hurting. She may have fallen and hurt herself, or eaten something sharp. It's very very important you get her to a vet, as this is NOT normal behavior.