If she did drown the rabbits, she should be charged. Unless someone found a policy from Petland saying "The way to euthanize rabbits is drowning", it's not the store's fault that she drowned rabbits.
I don't support any pet store that buys from puppy mills(and that's almost all of them). So for me, all the Petland's I've seen that carry pups are not on my list of places to frequant OR buy from. If someone wants a puppy, I can usually refer them around to breeders rather than pet stores.
Ditto on the peta link, didn't bother to click it.