I am not convinced the family liked the clutter so much as that, after Mom got attacked like that, they became invested in making her feel OK about herself. And Ellen, sweetie, if you really wanted to do some good, a gentler approach would have done more. The attack just put Donna on the defensive, and once someone is there, they are too busy defending the way they are to be open to change. I'm not sure how much Donna could change without some medical intervention, though, because I agree that this is probably a disorder.
And if that's true, then Ellen's shrew act was even more unacceptable. You don't rip into someone who has emphysema for coughing, and someone with this disorder is sick as well.