Background: After recruiting Wyll in Act 1, I (like many others) made the mistake of following Zevlor's advice to kill the Druid Kagha. This triggers the Druids to seal off the Emerald Grove, and subsequently meeting and interacting with Karlach then means she will not join your party. Nothing uncommon here so far.
Pre-patch #5, several players reported that they could (i) recruit Wyll, (ii) kill Karlach without interacting with her, (iii) travel to camp and inform Wyll that Karlach is dead, (iv) long rest --> Mizora awards Wyll with new magical robes, and finally (v) Resurrect Karlach where you killed her and then interact with her to make her join your party (details
here). Unfortunately, this no longer works after patch #5, as Karlach cannot be resurrected once Mizora has rewarded Wyll.
Here is what I did after the Grove sealed off:
1) Killed Karlach from a distance without interacting with her first
2) Brought her corpse to camp, informed Wyll that Karlach was dead --> journal updates and suggests you take a long rest (to meet Mizora and get rewarded)
3) Resurrected Karlach inside the camp with a scroll of revivify, did not talk to her after. She happily walks around camp.
4) Long rest --> Karlach and Wyll argue with each other, and you can decide to spare Karlach. Wyll then comes to terms with this, and if you talk to Karlach afterward she is happy that you talked sense into him. Wyll's journal changes from saying Karlach is dead to that she is not and that he has failed his mission to kill her. NOTE: Karlach is NOT recruited as a companion at this point, but appears with a green marker on the camp map.
5) Next time you long rest, Mizora will appear and punish Wyll by giving him devil horns.
After the cutscene, both Wyll and Karlach appear with exclamation marks over their heads and want to talk to you. However, Karlach will start to run towards the borders of the camp and will disappear from the map if you do not stop her. Despite the exclamation mark, attempting to interact with her then she will only tell you "Later"/"Not Now" and keep running. If you shoot her down and resurrect her then she will happily wander around camp again with a green marker, but if you try to talk to her she will again tell you "Later"/"Not Now" no matter how many times you long rest and/or leave and return to camp.
Alternatively: you can kill Karlach after the argument she has with Wyll in camp (point 4 above), but then during the next long rest Mizora will still arrive to punish Wyll instead of rewarding him.
This may be an odd corner case (and I admit, it is my mess really), but I find it a bit disappointing that no matter what I do after Wyll and Karlach argue (point 4 above), I cannot seem to get Wyll rewarded or Karlach recruited no matter what I choose to do. The outcome either way is that Wyll gets his devil horns, and Karlach dies or remains an NPC. There is no way for me to change the journal entry for Wyll saying he failed to kill Karlach unless I succumb and reload a previous save before the two interact and I lose 8-10 hrs of gameplay.
