I like it as it is, there is a high value reward,
the gem for the evil book that eventually gives you a very strong ability
but even if there wasn't it'd be good, it's optional, out of the way and clearly signaled that it will be dangerous.
If it wasn't as strong it wouldn't be an achievement to beat which is, optional boss rule #1
You don't need to exploit or even use mechanics, it's not unwinnable it's just hard and again, entirely optional.
I assume the intention of her isn't to fight but sneak around to get the spoiler and out again, but having it there as an optional very hard fight is great. Not everything needs to be levelled to the player in PnP or video games.
