similar happened to my sis and her 3 kids. Let us just say that they sued them and recovered the money for bites, hospital visits and stuff.
She should not be allowed to keep a dog if she can not control it. it could have been a little kid or a baby.
Till today, my niece starts screaming when she sees a dog. She was bitten by an unruly dog at the park whose owners did nothing to stop the attack.