A Sorceress Comes to Call (original) T. Kingfisher

Cordelia knows her mother is unusual. Their house doesn’t have any doors between rooms, and her mother doesn't allow Cordelia to have a single friend—unless you count Falada, her mother's beautiful white horse. The only time Cordelia feels truly free is on her daily rides with him. But more than simple eccentricity sets her mother apart. Other mothers don’t force their daughters to be silent and motionless for hours, sometimes days, on end. Other mothers aren’t sorcerers.