Why is my friend so Disgusting?

Okay, so a friend of mine has some issues and another friend and I were wondering if she possibly has a mental disorder.

First of all, shes disgusting. She showers maybe once a month, doesn't brush her teeth, doesn't bother with deodorant. She wears the same clothes all the time (not because she has none, my other friend is her roommate, she just doesn't like to change or do laundry). She smells and she doesn't care. Everything she touches is gross because she never washes her hands and she gets sticky. Not only that, instead of blowing her nose in a tissue, she blows the snot into her hand and then licks it up. Furthermore, she injured her big toe over five years ago, and its been infected ever since. She picks at it constantly and makes it worse. We've even caught her chewing on her toenail. She doesn't do these things for attention because most of the time she thinks we aren't looking.

Shes a slob in other ways as well. She leaves her dirty clothes on the floor, where she takes them off. Her bloody socks (blood from the aforementioned toe) will lay in the same place forever. Her roommate doesn't want to touch them for obvious reasons. She throws trash on the floor of her apartment instead of throwing it away, even when the trash is two feet away. She, uh, leaves excrement on the toilet seat, just because shes careless when she goes to the bathroom. (Not a lot, more like skid marks... on the back and Front of the seat...). My other friend who is her roommate is sick of it, since she has to live with her. Every time she tries to say something to her, she gets angry. She then makes my other friend feel bad about saying anything (shes sort of meek, and passive aggressive). My other friend is also worried because the disgusting one insists on cooking dinner and she never washes her hands.

So, now that you've read all that, are there any disorders that cause people to be that way? Could she talk to someone that would make her be less disgusting? And of course, I know a lot of things I could say to her, but I don't talk to her that often. I talk to her roommate and shes not mean enough to say what needs to be said. We're just curious what other people think we could do to actually help her. She also has issues with depression and we worry that if we just alienate her, she'll get suicidal (its happened before).