I always thought XF truly loved Ah Zhu and not because of guilty conscience - just that JY' cruel hand forced XF to kill his love, but repaid XF in the form of his reincarnation, GJ, who didnt have such bad luck
though the falling in love did seem rather sudden, but thats the way it is with XF, his emotions can run amok like a light switch - blood brothers with DY after a few drinks, suicide, going after Duen Jing Sun without careful questioning
CC maybe u should read the book a couple more times to wash away the adaptations