In the fight to protect Isobel she doesn't even count as your ally.

So number one, my fireball can't avoid her with Sculpt Spell, despite my clear interest in doing so.

Number two, she will calls out my rogue's current location to the enemies, stopping him from hiding.

And number three, she only uses mage armor after all the active threats I.E. the nearby enemies who want to pummel her, are all dead, when that's the first thing she should do in the fight.