Bush got into Yale because he was a legacy student, as many that go to ivy league schools are. And in fact, for three generations with the Bushes, they all led almost the exact same life while at Yale.
George Bush never proclaimed to be something he wasn't for personal gain. What reason would Warren have other than that? Would Harvard have hired her and paid her $400,000+ to teach one class if she was something other than a Native American? No way!