When I take my kids with me to the vets, I tell them before we go in not to approach any of the animals. This was not a dog walking down the street. It was a dog at the dog hospital. While the lady might have yelled a little help here, the mother wasn't paying any attention and yacking on her phone and OP was trying to get the woman's supplies. The owner was controlling her dog, the parent was not controlling her child. This is a place for pets, most of whom are scared, sick, hurt and I would no more as let a 4 yr old be unattended there as I would let the child play in a parking lot. And as a parent of 2 legged and four legged kids, I vote the mother was the problem here, not the pet owner, especially because she kept her dog from eating the child and did not lose her temper and scream at anyone.