I don't think she's playing with herself so much as she just found that position most comfortable to lay in
Nah man, that'd become super uncomfortable pretty easily no matter who you are. Your legs would start cutting off circulation to your arm if its squished between them and has the dead weight of one on it. Rather than finding it comfortable, she's just so out of it that she ended up like that without noticing, and soon when she snaps out of it her arm will be all pins and needles. Then, she can giver herself a "stranger." For the uninitiated, that's when you masturbate without having feeling in your hand so the only sensation you're getting is like someone else touching you (and pins and needles in your hand, honestly it doesn't sound that fun).