Just my luck.....

[Danny Boy]

First of all sorry if what is am saying might sound offensive but I can not be certain if your story actually took place or not. but even if it did... the screaming could be caused by intensive dreaming or it could even be caused by schizophrenia or some other mental disease. the cuts... I don't know, I haven't seen the injuries nor the place where she got hurt, because only by your description it could very well she have got hurt by something sharp on the bed. another possibility is the power of suggestion. for example women that truly believe that they are pregnant, even though they in reality are not, they will still feels the effects of being pregnant, feeling sick, belly starting to swallow, hormonal changes, etc. The power of suggestion is usually stronger in women. (its what i herd from a scientific documentary, they might be wrong, and sorry if I am wrong as well).

So for example if you friend truly believed that she was possessed, her "convinced" body would react as if she truly was. for many ages (and still in the present day) the Christianity usually perform their "exorcisms" to people who have mental disorders and should go to hospitals, some of them are just people that truly believe they are possessed but in truth they are not,but they think they are sso they attend to useless rituals that do nothing for them, other then giving them the illusion they are cured (again whit the power of suggestion).

I don't know the case of your friend personally, I don't even know if you are saying the truth or if you are just trolling (no offense). but what I just said is all I could say from the little information you have given me.