The divine soul that was cultivated by the Half Saint of Spiritual Power and the one by Half Saint of Martial Arts were very different.
When a monk of Martial Arts achieved the status of Heavenly Realm, he would be able to control the True Qi in his body and purify his soul. His soul would grow stronger and eventually evolve into a martial soul.
When the martial soul had grown stronger to a certain level, a divine soul could be formed by combining it with rules of Holy Road.
That said, the soul of a Martial Art monk was the soul of his own self.
Soul of a Half Saint of Spiritual Power was created out of nothing. When one's Spiritual Power had achieved a certain level, his spirit, energy and soul would be separated from his body and formed into his own unique divine soul.
That was the reason why, when the saint heart of the Saint Lady was repressed by the evil spirit of death, she became an ordinary mortal who couldn't defend herself.