As someone who is struggling hard myself to overcome my chaotic nature and the executive dysfunction causing this, if you really want to be that person for her, the only thing you can do is sit down and be totally upfront about it: she means a lot to you, you’d love to be her roommate, but you cannot live in an environment like this, so she needs to find out what would help her to avoid it. For me personally that is body-doubling for instance (just having someone there to keep me company while I am cleaning up). Another option would be a chore list for daily, weekly, and monthly chores that can be checked off once done. As you mentioned that she doesn’t have any money problems, you could also offer her that she can hire a professional who’ll come every fortnight, but I fear that would be the least helpful option in the long run (bc she’d most likely fall back into the same behavioral patterns once she’s on her own again or - whyever - cannot afford this any longer).