[spoiler] Amabel Swanson. I feel bad.

[Bek]

I prefer the theory that Clarence created the illusion that she WASN'T infected (after you killed her - for memory the screen even fades to white for a tiny period) so she actually was infected which does make sense. You never saw her on webcam for a reason. This means she is attacking you, Clarence can't actually hurt you, therefore she must have.

one possible hole in this theory is that she should have been able to communicate with the other infected in the shelter to come back her up, but tbh I believe that's just a gameplay decision.