We are using the advice to yelp and offer a toy to bite, ok and we only have had her since Friday, but I am worried. I never had a dog before and biting really, really scares me. She plays but it hurts and she cannot be near the children at all at this point. She's a rough collie and everything else is going well (taking to the potty spot and goes on command now). How long does it take for a pup to learn this?