I've been reading "John Constantine: Hellblazer" bit erratically and it seems that I'm missing some information about succubus Ellie that even the Wiki doesn't provide:
Constantine and Ellie had quite good relationship: John helped to deliver her baby and later helped her to hide from the First of the Fallen by etching a sigil in her soul. She was the one that back-stabbed the Devil and made him mortal, although she had to go into hiding (while still partially protected) when he came back.
Then John makes a di#$ish move and seduces Ellie (oh irony) to gain more power and reduces her protection to last only as long as he lives, in revenge Ellie manipulates his friends and girlfriend to abandon Constantine. Getting desperate, John makes deal with FotF, sells Ellie away and the last we can see her she is tied down in hell and her mother, First's lover, promises to bring her through most horrible tortures imaginable.
What has happened later? Wiki suggest that she teamed up with Constantine again, but the whole episode of being punished for attempted coup is strangely omitted.