There was a conversation with Withers where he shares a bunch of back-story about some of the big bads. He’s speaking pretty plainly, but there was still a dialogue option that said “Stop speaking in riddles and speak plainly. Can’t you give me more information?”. I felt like I had already obtained what I needed from him, but clicked that option just to be sure I didn’t miss something. The game zoomed in on his face and he slowly and firmly stated “NO”. I cracked up in real life because it felt like the “speak plainly” option was there entirely to toy with the players, which is pretty funny.
This happened to me and my friends two sessions ago. We ended up reloading an older save since it seemed as might lose a lot of story threads otherwise.
Indeed, depending on various conditions, quite a few threads can end there on the spot. Other consequences (like losing the necrotic resistance) can be severe, too.
As is, I think the fight is probably too challenging considering the stakes. From what I can tell, her gloves have been bugged since launch, and the fight was likely balanced around them being active and auto-clearing her debuffs. Last time I was there, she got paralyzed early in the first round and they made quick work of her after that (and this was a multiplayer session on Explorer).
Sanctuary does make the fight all but trivial if there’s a cleric in the party.