I would also adjust the price based on how many she is walking. If it is one then remember that you are only making $20 a day or less and that includes giving snack. If it is more than one then you can increase the amount and share it around such as $5 plus $1 per extra child or something like that. That is still a minimum of $25 a week spending money for the girl which will seem like a fair amount as in don't pay more than you need to.