What is the ruling on loving one of the Prophet's wives (peace and blessings be upon him) more than the others, and sympathizing with her?

There is no harm for a Muslim to love one of the wives of the Prophet, peace and blessings be upon him, more than others, such as Sayyidah Khadijah, may Allah be pleased with her. The Sharia did not obligate preference in love except for Allah and His Messenger, peace and blessings be upon him. The Prophet, peace and blessings be upon him, preferred Khadijah, may Allah be pleased with her, over his other wives due to her great role in supporting his call, and because she was one of the best women of Paradise.