If you honestly think you're not controlling her life, then I pity your empathic ability. I do wonder how you would feel to only be given limited access to a phone to be able to talk to your children who you only get to see once a year.
Your maid looks after your children 6 hours a day, 5 days a week, and lives on your property? Besides you and your husband, her influence will be the second most prominent in your childrens lives, and to think her presence will not contribute to shaping your children is a little naive. Continue to deny it all your want, but that maid is helping you raise your children, whether you admit to it or not is irrelevant. If you are treating someone who cares for your children like a restrictive business relationship only, then I wouldn't expect your maid to treat your children with anymore care and affection than that either.