You're lucky you were at Outback, at high end steak houses they will refuse to cook it past medium and will shrug if you decide to leave in a huff. They care more about their steak than they do you.
In my opinion, a 12yr old is old enough to eat undercooked beef. My son is 3 and he eats steak medium although I haven't given him raw fish yet. But since this is not your daughter then there's nothing you can do, it's all up to the Mama so get over it.