This could be very dangerous. Do you know what breed the male dog was? My husband had a small dog (years ago) that went into heat and got pregnant by a much larger dog. She ended up with nine puppies, three were stuck and died before they realized and did a C section to save the other six.
I am not sure but I believe that most breeders prefer bigger females and small males to try to make small chihuahuas because of the danger to the female. PLEASE get Sadie to a vet if you haven't already.