Hi, I'd like to help you with your question.
The best option for your friend is to seek out treatment through psychotherapy and possibly medication. However, your friend needs to see her hoarding as an issue before she may be willing to seek help. Commonly, people who hoard do not see it as a problem and therefore do not feel they need treatment.
You mentioned that you tried talking with your friend. Since she is in denial, you may want to try again with her husband. Spell out how the hoarding is affecting her family, her marriage and her social contacts. Do it in a nice, even tone and don't accuse or do anything you feel might make her defensive.
If you can get her to go to therapy, offer to go with her the first time for support. Or her husband may want to go.
Since hoarding is just becoming recognized as a disorder, possibly set apart from Obsessive Compulsive Disorder, treatment is still difficult since there have been few studies on what works and what does not.
Here is a book that may help you. It is called Digging Out: Helping Your Loved One Manage Clutter, Hoarding, and Compulsive Acquiring by Michael A. Tompkins and Tamara L. Hartl. Amazon.com has it or you may be able to find it at your local library.
I hope this has helped you,