It's one thing to live for years undetected with a fortune of $12.7 billion dollars. It's another to do it as the 77-year old daughter-in-law of the late, pneumatic, reality-TV phenomenon Anna Nicole Smith. As to how a 77-year old could be the 'daughter' of someone who, if she were alive today, would be 44, is a question we'll get to in a minute. As for how the 4th richest woman in the United States—whose $12.7 billion puts her behind only three other women--could have escaped detection until now by billionaire-hunters, Peter Newcomb, editor in charge of the Americas for Bloomberg News's Billionaire Index, has an explanation. "She's extremely low key," he says.