Huh... possible. Then again, Emhyrs is not a monster. Ruthless and uncompromising, yes, but he cares for his empire and the people in it... destroying the North just to beat his daughter into submission would be a bit below him.Very true.
It's also possible the Emperor made a carrot and stick sort of situation. "It'd be a terrible shame if I had to kill every tenth person in the North because my daughter wasn't there to rule them fairly."