That episode was a logical mess, Sansa waits until the last moment to show up with a larger army to change the tide of battle, (a rare occurrence in fantasy battles) instead of telling Jon about the Vale army beforehand, they could have used their numerical advantage to barter for Rickons life instead of letting hundreds of people including the King in the North die.
Seeing Sansa turn into a sadist was disturbing, maybe this is a darker chapter in Sansa's arc and she will become more ruthless like Arya from now on, or more likely they are satisfying fans raging revenge boners for Ramsay. revenge killing, especially Ramsay's brutal and ironic death is meant to be disgusting, not gratifying.