I think 10$ an hour sounds fair. But ITA that she should save some for the school year. But make sure (from expirience) the job doesn't overtake her summer and she still has free time with friends. I can't believe shes already 15! That way she can buy her own juicy bags. ROFL
I think a good way of thinking about the situation is what the comparable service this person could get for effectively $500/week ($10/hr x 50 hrs)? If babysitting + cleaning + having someone that she trusts would be more than $500, then your daughter is charging a reasonable rate. And heck, I know a lot of college students that would love to earn $2000/month.