Are you in the states? In the US, it is regulated by each state. In my state, you need to be licensed to work on clients in a salon whether you are doing their hair, nails, makeup or skin care.
Some states require you to have your cosmetology license or esth. license. I know at least one state has a specific make-up artist license.
I would be surprised/intersted if there is a state in the US that would allow you to work in this manner. If the owner doesn't know the answer, she/he (or you) should check with the state board as you could both be subject to fines among other liabilities including putting her/his license in jeopardy.
The fact that your mom works there would be irrelevant.