How terrible to raise pups to 8 and 14 weeks, don't quite understand why the 14 week litter is still there, even toy breeds go at 12 weeks? What a shame the 14 week litter did not go to their homes immediately after the second vaccination, as according to your friend the first pup fell ill within 4 days after 2nd vaccinations.
When you first wrote I thought it may be a reaction to the vaccine, I know one of my pups had his booster when over 12 months and had a terrible reaction to a different vaccine previous used, he was so ill within 20 mins he needed to be carried out of the surgery and was ill all day, some pups have died re: a reaction to the vaccines, it may be possible there is something in the genetics that causes a terrible reaction, or something in the manufacturing of the vaccines, I hope that this is also being checked out by the vet.
Vets don't always get things right, not always their fault, sometimes things are not apparent at the time.
Why oh why with this worry of Parvo in the first place were the pups not in an enclosed area, your friend has gone to all this trouble months in advance yet not made an enclosed garden area that no-one or nothing else can get to. If I had had all these previous worries I would have bought or made an oudoor kennel run for these pups to play in.
I'm so very, very sorry for your friend, what a tradgedy, completley and utterly heartbreaking to raise the litters this far it is devastating, if foul play is in fact found to be used here, I hope that proof can be found and the perps made to pay for the cost of the litter including compensation, but it will be so hard to prove, the antifreeze bottle may well have had fingerprints on it, if the pups are found to have antifreeze in them it may well have been proof, otherwise she can never prove they did it. Why just the pups though, it makes no sense. How could anyone ever hurt pups.

I will hope and pray for her that some pups will be saved, but otherwise I honestly would look to other breeders to raise her litter for her next time, does she know anyone that would be willing to help at all. Anyone in her breed club? It's the only way I would personally ever breed again, something is badly wrong here.