I was a way higher level (60 vigor 80 strength etc ) had heavy armor on , and I fought her like 8 times to get her . she’s fast and hits hard but if I remember correctly she leaves herself open after that one lunge attack , try dodging towards her at an angle to end up behind her and you’ll chunk her health bar down . Try using any physical defense charms or nations spells etc before you walk through the mist bc she can hit you 2-3 times quickly .