Coming from an extended family which seems to have hoarding hard-wired in their genes I am sad to say you, as an individual in their life, are fairly helpless to make changes to the situation. They will only change when they want to change and that has to be their decision. I can tell you from experience pointing out the problem and offering to help "clean up" pretty much never works. Being there for your cousin when she needs you is probably the most beneficial thing you could do as hoarding eventually does lead to people cutting off their ties to other people (either because of embarrassment or they won't go inside the house or whatever.) The best thing for your cousin would be to see a psychologist, particularly one that specializes in hoarding issues, and go from there. Improvement is possible.... but don't bank on it. It's a very difficult issue to tackle.