Got bridal caeda on my free summon but...

I got a bit of an Idea
Since when you refine her tome, it basically becomes a defensive light breath that boosts your and you allies defenses, I was thinking about running Fury, Watersweep, Some C skill, and Phantom Speed with her tome speed refined
Basically on the player phase she can attack mages or whatever without getting attacked herself, and then she and her allies receives a free +5 boost to their defenses
This +5 boost can help out, mainly on the enemy phase

It's unfortunate, but it's not game breaking for her, a simply but effective way to build her would be an enemy phase special tank with glacies. You would do that by refining her weapon to grant resistance, if you have the means for it, you could giving warding stance or warding breath. Her B skill could be a breaker skill of some sort, or perhaps even dull magic 3. Her C skill is also pretty flexible, but because we're building on her resistance, you could give her a ploy skill, like resistance ploy, or attack ploy. The same could be said about her sacred seal as well, but you have other options such as Fortress resistance, distance defense, or a simple res 3 seal. That's personally what I would do, but that is just a recommendation.