She was off colour on Tuesday, and Wednesday night she started being sick and diahorea.I took her vets Thursday and she was put on IV and given antibiotics.
What are her chances of survival and how long will it take before we know. I'm so worried

At twelve weeks old your pup hasn t really got a well established immune system. I know you are worried but you really have to keep in touch with your vet to see what the prognosis will be. If your pup survives and before she comes home you have your work cut out for you disinfecting your house, your yard area of any feces which will reinfect and is completely viral.

How can I disinfect an area contaminated by a dog infected with Parvovirus?
There are many Parvovirus disinfectants on the market, but regular old bleach is still 100% effective against Parvovirus. The dilution for bleach is one part bleach to 30 parts water. Caution is advised for dyed or colored fabrics or objects.

Puppies have the hardest time with Parvo. The virus wreaks havoc with the lining of the intestines, giving toxins and bacteria access to the blood. This toxemia and septicemia along with dehydration are the major causes of death as they affects all the other organ systems in the body, and is fought by the antibiotics and other therapies received at the vet's. A young dog' system isn't really equipped to handle such a disease easily, and severe forms of the disease cause high mortality and rapid death, but the most common, less severe form produces quite a respectable survival rate, as much as 90%. There is a cardiac form which attacks primarily the heart, causing atypical signs of discomfort, breathing difficulty, and sudden death in puppies generally younger than 12 weeks. It is thought these pups were infected in utero or as newborn.

One possible benefit in surviving a full blown case of Parvo is the chance of lifetime immunity. This depends on the pup's immune system, but at 12 weeks, it is functioning. Maybe not as fully as it may later, but it works. Any time a vaccination will create an immunity, the system is working, and obviously the pup didn't have enough maternal immunity to protect it, so you may have a fully immune puppy (to Parvo at least, still need Distemper, etc)when you get her home. Here's hoping.