they cast magma bolts, flying shards, and fire and iron darts as well - those could certainly be used.
edit: ok, i tried another run through, where i delayed the tuatha from showing up at the ulmish line for a few rounds, and the smiths happily targetted her for one round of spells, and then stopped
perhaps a calculation is being done that they will cause more harm to their own troops w/ thier spells - though the AI seems happy enough usually to kill its own ;p
yeah, when she's not surrounded, they seem happy to target her