There is no such law. But it is a lot of work and if the boss isn't willing to pay for the time, work and materials, then the boss shouldn't ask for it. LoupEsprit doesn't say whether the boss is paying or not, so we can't know.
However, if the boss is not paying for the work, the boss put the mother/aide in a precarious position with this request - damned with doing it every year she works there if she does it once, and doubly damned if she doesn't because she can be considered uncooperative by her boss and fired.
That is the only true problem I see with the request, and I only consider it a problem if the boss isn't willing to pay for the work.