I too babysat from about 13 or so and now that I am a parent I am amazed that these women left me with their kids when I knew nothing LOL. But I knew the kids and mothers quite well and they had seen me interact with their children from early on. I would visit them and hang out with them after school and on weekends as I lived in small county town and had no friends in close proximity. Maybe if she hasn't already, get her to come over for a couple of afternoon's to get to know your kids well first. Sounds a good idea especially as her parents are close and you would not be far away.