"Halt! I order you to... oh, forget it."
If this curse won't break even for sorcery and this thing is willing to attack the magistrate... well, it's regrettable but it's time to be direct. With a grim look in her eyes, Millie follows the smoke-creature, rifle ready and true. Multiple crisp reports echo out across the square, with a faint fizzle of arcane energy as new magical circles start to rise around the firearm. Mystical targetting aides. With their assistance, Millie couldn't hope to miss outright.
(1d20+4) Attack. (also + whatever AC this thing is)
(1d8) Fray damage. Commit Effort for Wizard's Wrath to guarantee it's a valid target.
Also brief note, Millie's intent was to Cast Quickly not Cast Instantly. There's not much of a difference when using a base level Invocation, but IIRC I'd have to commit effort for the day to cast instantly whereas quickly just commits it for the scene. (and doesn't require a damage roll unless it's actually successfully dispelling Theurgy.)