It not only depends on the dog, but also, many dogs will be VERY different at the shelter than when you take them home. I remember Jenny was very timid at the pound, she didn't eat anything, she was pretty much a different dog.

Many wonderful dogs are rescues, actually, I think (JMO ) rescue dogs are actually better in personality than non-rescues.

Some will bite, but it would be irresponsible for the shelter not to tell you so before you adopt.

IMO, what you mom says is not true. ( I'm not making much sense, am I? ) some dogs will bite. Some rescue dogs will bite. But ALL dogs will bite if they are not pleased with their circumstances. You could get a dog from a breeder that would react to storms the same way a rescue would.