There was a fantastic outpouring of enthusiasm from people all over this country, from all walks of life and, surprisingly enough, even from people from other countries. Itwas very touching to see that excitement. It doesn't take long for the steeliness to emerge from Supreme Court Justice Sandra Day O'Connor's apparently gentle manner. As the conversation strays onto a subject she dislikes, she firmly chops it off."I don' think that would be appropriate," she says, and a taut smiles ensures that, suddenly, you don't think it would be, either.Arizona's favorite daughter already is setting a precedent by granting an interview, not encouraged among Supreme Court justices. But she almost is bound to be a trend setter: the 102nd person appointed to the highest judicial branch of U.S. government, and its first female.Justice O'Connor's record after a year in office is characterized primarily by its conservatism. Apart from Chief Justice Warren Burger, the principal voice from the right is that of the court's other Arizonan, Justice William Rehnquist. In 139 decisions, O'Connor has concurred with him 123 times.But she also has joined the court liberals on some decisions, notable in cases concerned with sexual discrimination.She has attracted comment with her apparent leaning toward state power vs federal power.What caught her most by surprise during her first year was the volume of mail that greeted her."I was inundated with it in the early months here," she said, "far more than I had anticipated."