Hair, shower cap, lack of oxygen?

i have a friend who has gorgeous hair and when i asked her whats her secret she said she sleeps with a shower cap, but the shower caps she sleeps with DEPRIVES HAIR OF OXYGEN, doesn't that cause hair loss, i mean her hair is completely covered with a strong plastic shower cap and yet she gets amazing hair also she said she thinks its good for the hair?? any experts here on hair....depriving hair of oxygen isnt not good for the hairHair, shower cap, lack of oxygen?
I think that's a myth because you're hair is dead already and has no use for oxygen in the first place so depriving it would do nothing. I think what she's doing is coating her hair with a leave in conditioner and putting on a shower cap when she sleeps so that the conditioner doesn't wreck her pillow and her hair will get conditioned.