My first play-through as a Rogue (eventually trained into Warrior), I had to fight her 20+ times. Lightning Fist for me, and backstabs and such, literally having to load and reload if I didn't get a crit or she crit me instead of a companion. Second play three, Story Mode, for sure (I already proved myself), and Summons to hopefully have them take the hit. Not saying it's the best stretegy, but it's how I did it.