This is very sad.
But I must say, that the vet obviously made a very bad judgement.
How s/he could not see issues when she died so soon is unprofessional. She should have stayed at the vets to be monitored.
But maybe the vet doesn't care too much for stray dogs? Have you got a lot of them?
Not enough money in it for the vet, I suppose.
It makes me very sad, that still so many people care so little for animals, but I'm glad you tried to help, that does give me hope.