Use wither Yrden or Quen (depending on how good you are at dodging and flanking), but not both as you'll run out of Vigor very quickly. Like a lot of people have said, the trick is to get behind her and do 2-3 heavy swings, rolling away as soon as she starts to turn around. In addition to the oils mentioned, I would also recommend downing a Rook beforehand, especially if you use Incestoid Oil since the 5% damage increase from Rook will stack with the boost from the oil.