It is a great game. I didn't have any trouble with her, but then I was quite a bit higher level than you when I faced her. I was a heavy armor orc and all I did was bum rush her, completely ignoring her spells and just hacking away. I think it took me about 3 licks to kill her with TrueFlame. If good ol' hacking doesn't cut it, then I don't know what to tell you. I've never been much of a finesse player... I would try casting the golden saint, and then jump her like a duck on a june bug. Don't try to spell her, and don't cast hearthheal (it takes too much time, when you could be wailing on her) just jump to your menu and drink some potions at the appropriate time and see if you can kill her before she kills you. Do you have any resist magika potions or enchanted gear? That might help.

HTH