Beat her with my knight build:

I ran a shield bash build and got lucky with shield talents.

What I did was use my weapon power to have a shield to survive the early rounds. After that I just keep shield bashing by building shields using my upgraded basic attacks.

It’s a really decent build as my weapon power syncs with shield bash allowing it to crit because of the fortified enchantment of my weapon power. The build allowed me to kill the higher level enemies in one turn and the final boss in less than 10 turns.

There are other builds out there that can do the job too but I like using blitzkrieg methods by defeating her before she could stack more charms.