Many working dogs (gun dogs) do this, as they've been taught to hunt, point and retrieve, but dogs specifically used for this seem to've adopted an in-born habit, so some breeds are easier to bring on than others. Examples are, as you say, pointers, retrievers and spaniels, but other types can be taught how to do this, so perhaps your little dog has some of this in her background. Also make sure that she's walking and running about OK, as she could have something lodged in a pad, or to let your vet have a quick look.