I think that it's the girl sitting with Yeoryeong right now. She did leave at the perfect time to get the phone call and she could've given the other girl Yeoryeongs number.
All I can imagine is that's Nyuget for reincarnated into an alternate version of the story where Hitomi was a guy. Or the movie was based off of something where Hitomi was originally a guy and they changed it in the movie Nyuget starred in.
Ok.
The 999 souls probably have already been taken since its not like Eleanor had any choice when the people collapsed soulless. It was the slums and slums usually are overpopulated. I believe it was talked about how that was a pretty large slum as well. This also makes sense in Eleanor's reason...