I think the main issue is one of allowing the player to experience the fights.
If she ends up being as OP as she's made out to be (Aside from the fact that Ketheric seems to be able to easily just bind his lifeforce to her on a whim) then most people wouldn't get to experience the Ketheric Thorm, Avatar of Myrkul or Lorroakan fights as she'd just go and kick their butts herself.
That said, she could be made more appropriately powerful without being easy mode. For a start if she was invulnerable so didn't go down every 2 seconds (She's immortal. That's literally her most defining feat and why Ketheric valued her) she could then at least be a continual source of damage (Even if the damage she does isn't amazing).
