I think she's the original wife of the king, remember the legends about the lover of the king who sacrificed herself, so the legend continues and the king suffer from a pain, which relieves with the saintess power, but Nina isn't the saintess however the king feels a cool feeling from her different from the saintess, my theory is she can quench the curse of the king since she's the other half of him but her power is still not fully developed, however the reason why the king feels at peace with the saintess is because her power heals everything including the curse, so that is why she can heal the king but she is not the other half of the king.
I think she's the original wife of the king, remember the legends about the lover of the king who sacrificed herself, so the legend continues and the king suffer from a pain, which relieves with the saintess power, but Nina isn't the saintess however the king feels a cool feeling from her different from the saintess, my theory is she can quench the curse of the king since she's the other half of him but her power is still not fully developed, however the reason why the king feels at peace with the saintess is because her power heals everything including the curse, so that is why she can heal the king but she is not the other half of the king.