you need to stay out of thw water and use the lighting to attack her through the walls

Go across the first jump, turn right and wait for her to come to the water below you, just
shoot her dodging the occasional fireball/magic missile that she shoots up at you, most of
the curse/sleep is out of range and you just have to take a step back to avoid most of the
ranged attacks.

go to the top of the ruins and use magic and bow.