One can "get satisfaction" but we would not say, "get satisfied".
Say I have a grievance, a complaint, and I take my grievance to some authority. If they decide that my grievance or complaint is justified, and some action is taken to deal with my complaint, then by going to this authority, I got satisfaction.
Serena Williams is a professional tennis player, and she would need to be constantly practicing and trying to improve her game so that she remains a champion. If she were to allow herself to become satisfied with how she is currently playing, then there would be no need to practice long and hard, and very soon, some other player who does keep practicing is going to be able to beat her. So I would imagine she went on to say something like, "...become satisfied, I won't remain a world champion for long".