I have heard that invisibility helps and also you could blind her (if you have that spell).
Have you tried polymorfing her ? Just kidding as she probably has high spiritual resistance.
I just butchered her with my sword, yes and hellspikes helped a lot, as hellspikes have area effect, so when she was invisible I looked where her spells are coming from and cast hellspikes right away over there, after I heard her surrerings it was clear, I hit her <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />
You could try energy cage in a same way as hellspikes as well, and see if she resisted it or not.
Hope this helps.
