Is there anything I should be doing to help her?
The puppies were born on day 57 after breeding. They all died within 24 to 48 hours after being born. There was a place next to their umbilical cords that was open on every pup. One pup was born with intestines on the outside of its body.
What do you mean by normal? If you mean back to the condition she was in before she had her puppies, it could take as short as a couple weeks to as long as a few months. The uterus has to have time to "involute", or to shrink back to its normal size. Because she won't be having any puppies suckling, her body will naturally start to cycle again and she may come back into heat as soon as 21 days after she stops producing milk.
In response to the person who suggested you go to the vet to get a "milk stopping" shot so she doesn't get engorged: such an injection does not exist. Since she doesn't have any pups suckling, her body will resorb the milk and her mammary glands will return to non-functional status.
The fact that the puppies died could be attributed to a number of things. One of them is that the pups were born infected with a virus or a bacterial infection. These types of things can be transmitted through the placenta and/or the milk. Also, the pups could have been born prematurely. This is caused by the mother's body. Lastly, the pups could have been born with congenital (birth) defects that caused death. These are all clues that something wrong happened during the pregnancy. Many times, these are clues that the female should not be bred again.
It is best to spay your shih-tzu as soon as possible. This can be done even though she may still be lactating. Unless you are a reputable breeder and are substantially knowledgeable about breeding dogs, it is almost irresponsible to be letting your dog breed. I don't mean to be harsh but I've been a veterinary technician for 6 years and see this scenario countless times a year. The dogs suffer and later on in life have complications such as mammary tumors (breast cancer), pyometra (pus-filled uterus), and ovarian cancer.
I would strongly suggest reading up about the repercussions of uninformed breeding and to spay your dog as soon as possible.