Do you have relatives that give you money for Christmas, or gift cards? Do you have any way of earning the money for yourself? If you can earn half the price of the game on your own, maybe you can persuade your mother to give you the other half so you can buy the game for yourself.
And also, what does your mother think about The Sims game? That's what you need to be concerned about. If you can convince her that the game is positive and harmless, then you should have no problem...especially if you just come right out and tell her that's what you would like for Christmas.
