Can't "kill" Merveil

[BunnyHelp]

Someone in my group ran straight for the boss room while I was stuck behind, killing random things in the cave. They managed to kill Merveil without my help and now im stuck with the quest to kill her but I cant, someone else did, the hole in the wall opened to the forest and I cant go through it without "killing" Merveil. Any ideas to fix this?

[The_Driver]

Join a fresh instance where she is still alive. To do so go to the entrance of the caverns of wrath exit towards caverns of anger. Click the caverns of anger entrance while holding ctrl and select new instance. Then run through as normal and end her reign of terror.

[Dree]

If your party members kill Merv while you are still in Cavern of Anger (not cavern of wrath), you still get the quest even if you are not in Merv's lair.