I see the two as the same thing, having her recruitable in both paths means she's a part of 100% of players story, not 35%, meaning theres a strong incentive to improve/finish/expand her character. Not either or, but A so B
That's fair, I just wanted to note the wild success Larian's had in getting people to not choose the obvious morally "good" path in a videogame. It cannot be overstated how absolutely unpopular it is, even in a series like Mass Effect where it's less of a moral choice and more of a color-coded attitude. And it's a massive shame that after being that successful in getting so many more people than usual to try out the less traveled path, a companion unique to that choice is just flat out missing most of her personal story and interactions.
Though honestly Larian already built in the best way to make her available to anyone following through with defeating the Goblin leaders/defending the Grove during the assault. There are at least a couple fights in the game already wherein a specific enemy reaches low HP, sometimes under other circumstances like at least one other enemy being dead, and tries to surrender. Since "Knocking Out" counts to the game the same way as killing does, just script a low-health surrender condition into her combat interactivity in the Temple or the Grove assault. After the surrender maybe you talk, but I think with her personality and skills she'd try to stealth away and end up in Moonrise regardless (and maybe on a successful perception check a player chooses to kill her anyway for trying to escape). It would play into how shattered her confidence seems, having narrowly escaped a more permanent defeat and would have no conflict with how her dialogue already plays out there. Xiphos's storyboard is nice, but probably more work than needs to happen to accommodate her availability.
But the most immediately important thing is that she just flat out needs to have her existing content fixed to properly activate in-game, assuming the associated voicework and scenes are also finished and in the files.