Re: sims 4 on two computers

Every game has 1 serial, when you and your sister want to play at the same time you need 2 serials, what means 2 copies of the game.
But you can play the game when your sister isn't playing the game and vice versa. And yes that needs to happen on the same Origin account the game first was installed to.

I know this is frustrating, but look at this from EA's standpoint. If you could play the game on multiple devices at once with just one copy, you could lend the copy to everyone you know. Everyone would have a free game to play, and EA would not make money. And would not be able to pay the amazing people that made this amazing game. 

I hope that explains it, and I hope your sister and you can work it out.