This is not only an interesting story, but also a hidden turning point in history. Had the then-Sandra Day married Rehnquist, she almost certainly would never have been appointed to the Supreme Court herself in 1981, even if she had otherwise had the same type of career as she did in real life.
By that time, Rehnquist was on the Supreme Court, and nominating the wife of a sitting justice would have caused obvious political problems. Reagan would have had to look elsewhere to carry out his promise to appoint a female justice, and whoever he picked might well have had considerably different views from O'Connor's on various key issues (federalism, speech, abortion, etc.).
By choosing John O'Connor over Rehnquist, Sandra Day (unknowingly) assured her place in history!