My guess is she learned about MC "death" and wanted to bring him back.
My guess is she actually made it
She couldn't find a way to revive him from the frozen body, so the 2nd plan was to "manipulate" his soul to a new body
And make sense, who would know who he is expect her. The books were given by her, and the "oops no more book" accident also made by her
Just the weird part is why ask people to search for a "gold boy" when she know who he is
Maybe for some reason order are delayed / from the past. Maybe the soul magic made her unable to move, that's why she use pets to deliver book ( and maybe steal the biography)
Also maybe the pets order were linked to the soul, that's why the pet could execute the order, but the black mage don't know who he is ( just know the town )