Try to remember that she is not becoming "aggressive." She's becoming more at ease and confident in her surroundings (your home), and engaging in typical Lab play. My adult Labs look and sound like they are killing each other sometimes during play sessions. First, hopefully your child is not laying on the floor with puppy. When they are at their level, they play with kids like they do with peers. You might try to have your kid incorporated into the training regime. Have kid help you teach sit and reward the puppy. Things like that. Keep a tether on puppy so quick corrections can be managed. That also helps. The children in my life were prone to squealing and running, which caused my dogs to chase them as puppies. I put the kybosh on that immediately.