It sounds like there's an underlying issue here possibly though, obviously I do not know your friend but has she always been like that? And hoarding on to old coursework for example sounds like more of an issue rather than being untidy.So i need to vent, one of my friends is so untidy. She has always been like it in all the years I have known her. Her house is verging on a hoarders paradise and there is stuff everywhere like EVERYWHERE. Her ktichen sides are piled up high with dirty dishes and random stuff. She hates cleaning and would rather do anything but tidy up. She works with me and her locker is jam packed full of junk, so much so that she has bags of stuff filled with old coursework(she quit it years ago) in different parts of the office. I have just been cleaning up and I'm sick of random rubbish lying around. How can people live in chaos?!
A couple of years ago my mental health was really bad, my house was a shithole. I didn't wash posts and had to chuck stuff away because they were that grim and full of mold (disgusting I know) but I was in a bad place and just so unhappy I didn't care and prior to that (and now) I am a clean person, I like cleaning and having a tidy home but that particular year it was difficult for me
Maybe try talk to her? Offer to help get rid of some of the stuff she no longer needs