XD Well, it's a good thing Florence and the rest of society aren't aware about that aspect of her life.
Okay, we can have them share a grandfather and make them second cousins, if you'd like. Is it known that her mother married a half-blood or was it covered up? Because that will change everything and Isadora will shun her rather than just be indifferent to her. If it isn't known, do you think they were friends during their childhood, if her parents were socialite Purist types?