about sierra I feel like I should say somethings:
the agriche are capable of abduction, sierra could have been kidnapped
it isnt like maria? mary? dion's mom? was actively physically aggressive to sierra, they probably enjoy it when sierra looks scared, the agriche are not ones to kill instantly, so its possible that they didnt kill her she could also have a hidden worth we dont know yet
and about asking her kids to be good agriche.. like what happened to her son ashil, if they don't become good family members they will get killed, if roxana didnt become an agriche she would have ended up like her brother, sierra asked them that for survival
honestly for someone "meek" she's still pretty sane, and her mental stability must be pretty strong? She can still interact with everyone somewhat normally tbh