You might also see about posting this on the subreddit if you haven't already just for more visibility because I actually love this idea. I've seen posts from people who didn't know where she was, so it's entirely reasonable that someone could miss her without metagaming, and I'd be lying if I said I didn't have my own issues with Alfira showing up to your camp at all considering she never seems to really entertain the idea of being an adventurer if you're Tav or any of the other origins. The only one that made any amount of sense to me is if you cross the bridge to the Blighted Village without going to the grove at all and she slipped out to find some outside help.
It just feels like they put too much effort into Quill to have her be relegated to what was meant to be a failsafe if Alfira is dead. All of the other characters that you only see if certain NPC's are dead, like Chell in the case of Alfira during the tiefling party, only exist to take up space and spew out one or two throwaway lines but Quill has a full on conversation with one of the few Dragonborn tagged dialogue options before act 3. She even gets brought up a few times afterwards, like the Dragonborn bard who mentions her only if you kill Quill. On that note, however, I would also hope that Larian at some point puts in reactions from your companions for Quill's death like they do with Alfira (i.e. Astarion telling you to be a bit more subtle next time).
