Her stats are fairly low for her cost. You're not going to be able to get her on the field too quickly and at that cost, why not just place a Mage? They'll break through defense too.
As usual, I'm cautious of units that spread themselves thin and try to do too much. We already have magic damage units to deal with armor heavy enemies. It's pretty rare that you have enemies that need multiple teammates to hack down, so I'm not sure how useful she'll be. Sure, maybe if enemies have high defense and magic defense she may have a place on the field, but eh. Remember that her ability is incompatible with Mages and Witches and all magic users too, so she kind of forces a certain playstyle to use her as effectively as possible (Gunners instead of Mages for starters).
TLDR: Seems like one of those units that seems good on paper, but will probably not be all that practical/useful in general. Of course you can come up with scenarios where she's useful, but I'm not seeing her being vital.
Still, I'll raise her, her skill alone is fairly useful and her awakening could be good. I don't think she's trash or anything, but I doubt she'll be a solid team member. It is nice that she could give you other options than being forced to have 1-2 magic duelists on your main team for armored enemies anyways. Having to keep Princesses and other magic allies on your team constantly is obnoxious at times.