Sentence:  In the middle of the room is a young Infanta intended for Marguerite Theresa, born in 1651, daughter of Philip the fourth, whose portrait Velasquez took in 1658, to send to Leopold, who had just been elected Emperor of Germanyd and who <WSD>mercied</WSD> her in 1666. 
Meaning of the word marked with <WSD> tags:  To show mercy; to pardon or treat leniently because of mercy