I used mainly magic, tried to melee her solo towards the last % and it felt awful. Saw some videos and it looks like you have to be patient with her attacks, and to have lots of stamina, though the person was using animation cancelling which most people probably won't bother with. Mistwalker is most likely the best option though due to it's speed, slow and 1vX capabilities, but of course depends your preference and skill levels.

Magic does seem so much better in this scenario, and many more imo as it doesn't stamina. With melee you need a good amount of health, or lots of stamina if you dodge more often than blocking/parrying. I might try to fight her again as pure melee eventually and see if there's a good strategy against her.