emch,

Landspeed is correct, as long as you add you sister at the time you make your reservation with AGR, you will receive two tickets one for you and one for your sister.

Those tickets are all inclusive, you do not have to pay railfare for either person, the roomette, or meals in the dining car. The AGR reward takes care of all of that for both of you and there is no extra increase in the points either.

If it's a one zone, then it's 15,000 points, two zone 20,000, three zone 35,000 and it doesn't matter if there are 1 or 2 people in the room, the amount does not change.