Yes but she can have them if you let her get pregnant.
With any dog, ages 6 - 7 is about it, for the dog's sake.
She might be too old or have scarring from previous pregnancies.
No, they are too old. If they do, you will be risking their life.
as long that that dog had puppies too
If the dog is intact (not spayed or neutered), yes 8 years old is not too old for a Chihuahua to be fertile and capable of having puppies.
The only way to tell if your dog is too small to have puppies is to ask your vet. Your vet will be very honest with you.
about 6 yrs
They are many risks of having puppies too early. Stunted growth, personality disorders, not good mothers, unhealthy puppies ect... You should always wait until a dog is over one year old before breeding.
it can be any number of years old
About 5-6 years old
You dog will stop sitting on the puppies when they are at least 4 weeks old.