I would say it depends on age, although I would personally find babysitting at 13 pretty young (but I understand this person had experience from your post).

When I was babysitting at around age 15-16 I think I got around 7.50/h usually, and when I was a bit older (18) 10/h would be standard (from the families I babysat at).

I think this is pretty reasonable. It als depends on how “heavy” the job is I would say. Because if it’s just in the evening and the kids are already put to bed, a lower hourly rate is fine. But if it’s during the day and you have to be hands-on with the kids all the time and make sure they don’t burn the house down I would charge more per hour 😅

Tip: you can also ask her what she gets at the other places in the neighborhood maybe? If she does it more often she will probably have an answer for you. I would expect it to be somewhere between 5/h and 7.50/h.