She didn't "realise" she was dead until after they left 3-4 through the portal and she became a ghost in the real world. Alis, who was really dead was actually okay.
If Alis us currently an undead at the moment, it would be strange that he hasn't shown any signs of degradation after 14 years without medical treatment. That said, for all the talk about "degradation" and all the people in Ai's village seemed pretty normal for me. You really have to wonder if it's necessary to disable them.