Hmmmm, I have another suggestion:
They have gotten angry with her. That is, something she said or did made them angry. Could this be the case?
Saludos
PD: now that I look more closely in the dictionaries, I might be the case that they have indeed mistreated her, or shown her no mercy, taught her a lesson etc. From Oxford: "se ensañaron con los prisioneros: they treated the prisoners mercilessly".