Show her the website Flylady.net. You could get her the book "Body Clutter" by Marla Cilley, but she's probably not going to read it...at least not now, anyway. Get a sitter or another family member to take the kids out of the house for a few hours so you can shine her sink.
Tell her the first day that all the two of you are going to do is shine her sink. If the kids are there, make a game of it and they can help pick up the garbage and put it in the trash. While you're doing the sink, light a candle. It's a pampering thing, it soothes the nerves, and it makes the house smell better! :)
Where's Hubby in all this? Is he tryiing to help out, or is he chastising her for the state of the house and complaining about how he doesn't get enough attention? In essence, making the problem worse by making her feel even MORE of a failure. (To be honest, I want to sue the marketing company for the Enjoli commercial...google it, if you are unsure what I'm referring to.)
I've been where she is...all except I didn't have insurance, so no medication. Flylady helped me learn to love myself, realize that I need loving, too, and that it's okay if I pamper myself and show myself love, especially if I'm not feeling much love (or help) from anyone else in the house. I got out of my depression, cleaned up the house, and taught my boys how to pick up and clean up as well. (They were 2&4 at the time.)
Take her out for coffee, lunch, shopping, whatever, WITHOUT the kids or hubby...go for a pedicure! It does absolute WONDERS for the soul...more than the soles! :)
She needs your love, acceptance, understanding, and unconditional support...she's condemning herself more than anyone ever could and my guess is that Hubby is adding to it.
I feel for her, and for you, not knowing how to help. I wish you the best in whatever you decide to do.