His will did not mention her. Although she filed a lawsuit, the probate court said that she was not in the will and therefore did not get his estate. Fortunately for her, a Texan bankruptcy court had already awarded her about half a billion.

It's not unusual for him to have left her out of the will. He also disinherited one of his sons, J. Howard Marshall III.

SOURCE: http://celebritynews.about.com/library/attitude/bl052801.htm