Where did you get the Alyssa being a Column/Pillar? There was 'Sarah Gallagher" who visited Haruka, (Nao, Shizuru, Natsuki, and the one with Akane are the others). There was a Miyu flashback that showed her through the window, but there was no indication she was a Pillar. The hair didn't match any of the Pillars, it looked like she was just an ordinary citizen.