I undertsand that you are worried about your baby. I have a Chihuahua too and they are sooo tiny.
I think Princess has acid relux. Give her a quarter of a pepsid ac (famatodine) in some food every ten hours. Twenty miutes late try to feed her.
She may have a bad tummy ache. I would pick up any dog food.Try a small amount of boiled chicken with all fat drained off, chop meat , or baby food with no onion, beef, turkey, etc
Go very slow so she does not throw it up.
Dogs get dehydrated and hypoglycemic very easily.
Add unflavored pedialyte to her water 50/50 to hydrate her and balance her electrolytes.
Put a drop of pancake syrup on her tongue to raise her blood sugar in case she is a bit hypoglycemic. That should perk her up.
Also give her one teaspoon a day of plain yogurt to keep "good" bacteria in her system.
If she develops any abdominal pain, bloating, constipation or cannot keep anything down she needs to be seen by a vet.
Please let me know how she is doing. I will always be here for you
I hope your baby feels better very soon..