Who is DeDee Ex and what relevance does she have to the lore?

House brings her up constantly. I'm really confused. At first I thought maybe DeeDee was some kind of alias for Stacey, but then I heard Foreskin talking about her, and I know for a fact he only likes Pursuit (we don't talk about 13, that's not canon to me because I say so). Is she perhaps a famous diagnostician? Is she Will's daughter? I'm having trouble following.