Druid stronghold issue.

[Niall87]

I can't kill Nilthiri during the first quest of the Druid stronghold line. Everytime she goes to ground all magical/fire damage gets reflected back at the attacker. I know there was a bug with the unfinished business mod for the original BG2, but I don't have that installed. I do have the BG2 tweaks pack installed, but I've gone through the list again looking to uninstall any script modules, but there doesn't seem to be any affecting enemies.
Is there away arond the issue?

[Hamtata]

easy.......drinking a potion of fire resistance and using a scroll of fire protection should bring your fire resistance up to 90 (or 100, i can't remember). and if you equip a ring of fire resistance, the reflected fire shield damage will heal you instead. The potion can be found in adventurers mart and scroll can be found mostly in any temples.

Seems to be related with unfinished business mod: https://forums.beamdog.com/discussion/25759/nilthiri-the-troll-shaman-cannot-die

[Caethyril]

I didn't have this problem, but I wasn't running any mods...

Acid should also work to finish off a troll, but I'm guessing that's getting reflected as well?