It's the reason she did it. Yes it was political, but it was to get a psychopath and his zealots because she was losing the war that she didn't need to actually fight.

It wouldn't be a any different if she went for the Viking girl's brother, because she wanted a fleet. The correct decision would have been to begin negotiating peace with Alexis, through Villar.

There's hints from the witch burning that the Mage's Association leadership is behind this entire conflict.