It's good to know the grandparents will be vigilant. Back in my day, my parents would never have left one of us alone with a relative stranger. But those were long-ago times when divorce and single parenting were not common. I think kids have evolved with changing times to know how to take care of themselves and their privacy needs. Although the older daughter is clearly not happy, she strikes me as a smart someone who can defuse a situation should she be in danger.