If your daughter is ordering items a la carte, and you give her 1/2 your steak, it is unlikely to be an issue. If she sits down, orders nothing, you ask for an extra plate, and then give her 1/2 of your appetizer, salad, steak and side -- that would be a problem.
But regardless, the rules apply to you too, so don't be shocked if you don't get what you want if it's against the rules.