It is true that if one of the eggs died, it would take care of the problem, however that does not fit the facts as known. You see, her genetic makeup is that of two distinct individuals with some organ systems of one and others of the other. If one of the eggs died, then it would not have contributed to her final state. In fact, if one of the eggs died, we wouldn't have the conundrum because she would only have the genetic makeup of one individual and be just like the rest of us.