I can't really give too much of an opinion on the vet tech's decision since it sounds like not everything is known yet (as per your questions in the letter you have written). I did though, want to express my sadness over the loss of a nursing mom and her babies. These stories are heartbreaking, to say the least.
Also wanted to add that one of the reasons I quit volunteering at the HC here several years ago was I could no longer take the administrative decisions that were handed out on many of the animals. Clean sweeps of the kennels used to be done upon one case of Parvo...all dogs kept in the same area were euthanized immediately, and any showing any signs of loose stool - for several weeks afterward - were also euthanized, despite the fact that there can be many causes of loose stool, including stressful situations. If an animal showed any sign of 'aggression' it was immediately put down. One case in particular was a beautiful older dog...he absolutely adored people and was a true sweetheart, but he did not get along with other dogs well. He'd been at the shelter for several weeks when one day two of the younger dogwalkers (volunteers) who were walking dogs separately (this dog and another) made the mistake of allowing the two dogs come too close together. One growled, and the other - this dog - snapped back. One of the dogwalkers, seeing a the signs of a fight starting, put her hand between the two...and at the same moment that the two dogs lunged toward one another. She was accidentally bitten. That was this beautiful little guy's death sentence...they brought him inside and euthanized him that afternoon.
It just tears at me when a healthy, thriving animal loses its life over such a thing. Many does - even relatively docile ones - will often protect their litter aggressively, taking hand movement as suspected threat to their babies. If this was the case, it's a tragic shame if this little girl was not assessed properly, and assumption was made that she was too aggressive.
My heart goes out to them all. :bigtears: