If your mom buys it on another computer in the house, it's fine. you can even buy it at your friends house, doesn't really matter.
but if you use your key at multiple houses, or IP dresses, such as you using it at your home, then using it at your friends house, it will be removed from the game.
BL_ID sharing is a thing you don't to.
but yeah, you can buy it and use it on anouther computer, just make sure they have the same IP address(witch they will, if it's in the same household)
