First of all Melissa I am so very sorry for losing Bella. You must be devasted and my heart breaks for you.
IMHO petsmart should be the last place that a small dog owner should take their dogs. I mean come on how much training have those kids had?? Not enough for ME to trust THEM thats for sure!!!
I hope you are taking action against them. They shouldn't be able to be so casual about it. and at the very least they need to have better training and way better policy about the dogs. Like big dogs on one day little dogs on others.
or small dogs at certain times of day and large dogs at other times.