As a holy mage, spam light attacks to daze the crap out of her. Put pillar of light on a wand, drop a temple of light and put up the lightning damage barrier. Even with no supporting temples ToL is a 1 mana daze chance or will knock off a Forcefield token without taking up one of your actions.
daze not only gives her melee attacks constant miss chances, but each one also gives her -2 to defense rolls. The damage barrier can stun her mid-attack even.
Also, direct damage bypasses Forcefield. Burns, bleeds, rots, ghoul rot,chains of agony, idol of pestilence and such will keep doing damage even after the shield is up. Stranglevine not only does direct damage but it also immobilizes her and can be cast even while the shield is active.
If you really wanna be a jerk, add in a giant wolf spider. It's psy-immune and can fire ranged stuck tokens on her all day so that she never gets to move into melee.