Well, in the scenario I imagined, it's not really necessary for
Jezera to kill Rowan - after all, he's a loyal and useful servant. But it is very necessary for
Alexia to kill Rowan, to really cement the betrayal

.
As for Andras, eh, exile's good enough for him, really, and presumably less rough on Jezera but... I have trouble imagining him accepting it. Maybe a desert island somewhere, or something? A nice one, too, just to rub in how she's going out of her way not to kill him. But, while Jezera probably doesn't want to kill her brother, the reader is another matter...