Complex sentence: Although she could have just been bluffing to manipulate him into helping her, by that time they had merged to the point that they each remembered everything the other said and thought; if she had been bluffing, it is likely that Ben would have known.
Split into simpler sentences: Although she could have just been bluffing to manipulate him into helping her, by that time they had merged to the point that they each remembered everything the other said and thought. If she had been bluffing, it is likely that Ben would have known.