if she had said the shahada, constantly questions the divinity of jesus, believes in the 5 pillars of islam, i dont see why she calls should call herself Christian! I think she probably just doesnt wanna let go of her christianhood where she had a lot of power since she was a priest.
as we've read, she was from a learned family where everyone was interlectually successful. knowing this from her background, i hypothesize that she is the kinda person who enjoys the position of "power". if she was to identify herself to be "totally" muslim, she would have no power anymore. instead, she would just be a member of a big family.
what i am guessing is that power means alot to her n she can only achieve that in xtianity.thats why she doesnt wanna let go of it ALTHOUGH she is a practising muslim.