Katherine Hester is an old friend of Boomhauer and ex-fiance of Boomhauer's brother Patch Boomhauer. She made her only appearance in "Patch Boomhauer." Boomhauer was shown to be still in love with her and her engagement to Patch broke his heart. When Boomhauer was falsely accused by Patch for patronizing prostitutes, Katherine despises him. At the rehearsal dinner, Katherine confessed that she's only agreed to marry Patch because of his resemblance to Boomhauer, whom she still has feelings for, and believes that he's patronizing prostitutes in a desperate attempt to get back together with her, so she decides to call off the wedding. Patch lets it slip that he hired the prostitutes to discredit Boomhauer to make himself seem like a "hopeless romantic". Katherine is outraged that Patch would have dishonored a blood relative and breaks off her engagement to Patch on the basis that a serious lie such as framing Boomhauer is two strikes already in a forthcoming marriage, and realized Patch is a real sleaze. She then leaves Arlen to clear her head, but before that she hugs Boomhauer and apologizes for misjudging him.
The guest character is the voice of Laura Dern.