Throughout the game, after Eileen joins you it is possible for her to get hurt, though she never dies. The more injured she is, the more possessed she is, and the more bloody she gets.

Healing

You can heal Eileen by using a holy candle on her. Light a holy candle and make Eileen stand over it. Eventually she will become less bloody. The effects are only temperary though, and once the candle goes out, Eileen's wounds will return. The only place I would recommend healing Eileen is right before going into room 105, of the apartment level, where Eileen will leave you. Only do this if you want Eileen to live through the final battle.

Different Cutscenes

There are two different cutscenes that are affected by Eileens health. The cutscene at the lobby of the apartment world, and the cutscene at room 105 of the apartment world. You can get 3 different cutscenes at each of these areas:
1. Eileen is healthy - she will act normal, not possessed at all.
lobby script; room 105 script
2. Eileen is in bad condition - she will act somewhat possessed.
lobby script; room 105 script
3. Eileen is in horrible condition - she will talk and act like little Walter.
lobby script; room 105 script

Conditions

1. Healthy - Eileen has very little blood on her.
-She will talk and act normal.
2. Bad - Eileen will be bloody.
-She will talk and act as if she was a child, or she will recite holy scriptures and talk like adult Walter.
3. Horrible - Eileen is extremely bloody, you can see little white on her and the blood is sometimes black.
-Sometimes she will stop and start beating on herself, mumbling stuff you can't understand (captions will read stuff like "#@%* &%#@&@% $%#@"), and other stuff. Everytime she does this if you go near her the screen will go red and Henry will be injured.

End of Subway World

Eileen will not become bloody until the end of the subway world. If Eileen is injured by enemies or Henry, after the cutscene at the end of the subway with Walter Eileen's injuries will all show up at once (if she was injured a lot she will become really bloody right after the cutscene).