Isabella as a pure LI doesn't strike me as very interesting. On the other hand, some scenes where you can humiliate Isabella seem much more appealing.
Isabella is a bitch. Yes, because of her past and blah blah blah. But she's a posh bitch after all. Having a romance with her... No, it doesn't appeal to me. But humiliating her and putting her in her place, especially if you're also blackmailing Britt, seems very interesting to me. You could even tell a redemption story there, having mother and daughter grow closer to each other as they are going through a similar situation at the hands of the same motherfucker.