I helped her in a different playthrough - that has its fun also.
I've only ever killed her in the goblin camp, I guess this video is from a playthrough where people let the goblins attack the grove but defended it? I guess the question is whether the issue is where/how you kill her, a saving throw, or whether the caster is coincidentally the one who struck the killing blow. Very interesting. Thanks for the link. Next time through I shall have to kill the Gith and see what, if anything, they have to say for themselves.