My parents didnt charge board while we were studying, but when we left school, we had to pay $50 a week if our pay was over $100, or half if it was under $100.

If its just an after school job, maybe ask her to give yu 10% of what she earns so you can put it away,, and save it for her, and she can do whatever with the rest (this is what my mum does with my sister, who works at the local woolies).

good luck with whatever you decide!!