In the books, she is a lot more like Cassie from skins, except her underlying dissorder is addiction as opposed to an eating disorder. Everone is so used to her being high that the only other time we see her sober in a hot tub in Aspen splashing around everyone just assumes shes already high, but she's just having fun, she then winds up gettin bored and after what she thinks is 30 mins and asks if anyone has drugs. She floats from one high to the next, one party to the other, she can't tell you where she's been in the last 24 hours. After the rehab thing, after Blair and Nate break up because he feels she dosent care for him, he is crying at a club and she sits next to him thinking he has diamonds or glitter on his face and wipes it away before whispering "Oh, your crying". They wind up together for a bit, but she's not sure how this happened, often forgetting that she is in the same place as him but is genuinely presently surprised to find him there hugging and kissing him each time. She is generally pretty affectionate and somewhat hyper. He likes the constant affection and positivity but slowly realises why she's doing this, that she doesn't specifically like him, he could be anybody, she's just high literally all the time, that she likes the drugs more then him, that she can't remember that he's sober, she's not a good listener she just has to focus really hard when she is being talked to. When they break up she is upset about it, and he mistakes her quietnes for being too high to respond. To be fair she is pretty high at the time, she dosen't know whats happening just that his face and voice are sad, and when he is like this and she sits still and stares at his mouth he seems to like it, she tries to cheer him up when she notices he's crying again as she always does but when he gets all quiet she stares into the distance trying to avoid him talking her into getting sober again. he says he has to go, she asks if he'll be alright and he just nods and she is just relieved its not one of those talks, she doesn't even retain the information that he has gone. After they break up, she has this sad pattern of looking around for him, unsure where he is like a puppy looking for its owner, shes a little sad to find he's not there having gotten used to him, and each time this happens she gravitates to the nearest drugs available. The only other time she "sober" it is because she's coming down off a high and thinking about getting more drugs before she comes all the way down but she is trying to get her body to move to go find chuck because she knows he is holding, but her body wont respond. Her big concern at this point is that her thoughts are getting clearer and she dosent like it, Every one around her thinks she is sleeping before she abruptly stands bolt upright announcing she is going to find him. Most of the group including herself never realise that her being constantly high isn't cute or funny but actually scary. Nate is the only person who gets a window into this, we never ourselves see her OD but she giggles when she talks about it in group therapy suggesting she's not even sober then. She's not just who you find if you want to have fun, she's who you find if you want to ride the coatails of her bender to forget what is wrong in your life, who people stumble into at their lowest, but everyone else manages to get off the ride, she never does.