Shinji is left behind, alone. Slowly, he gets up.
SE <<An alarm siren resounds from in the distance.>>
Magami No ER: Why does she go to HQ if she still can't pilot and basically does nothing?
Reichu: Shinji was originally sent as her backup, but now she's become his. If Shinji for whatever reason didn't comply, Rei certainly would have gone into battle instead, despite her injuries.
Beer Goggles: So did Rei know of the impending Angel attack or was it visual confirmation on her part? Maybe Misato gave her a cell phone as well…
Reichu: Maybe her Angel Sense was tingling. ::D