My mother has serious health issues. Her only income is SSD. She has no assets. Would she qualify for a nursing home?

I see from your profile that your mom is 56 years old and that you have a newborn. So sorry that you are both in this position.

Though your mom isn't technically a senior yet, I have the impression that many local Area Agencies on Aging can assist disabled adults as well with determining what services they qualify for. Here is the website for the Area Agency on Aging for Kootenai County:

http://www.aaani.org/

The main phone number is (208) 667-3179.

Medicaid requires one to meet medical and financial requirements. A NH is also called a SNF. Skilled Nursing Facility. One is supposed to need 24/7 skilled nursing care to qualify for a NH. A doctor would have to write an order saying she needed this type care.
The local Area Agency on Aging might be able to do an assessment and help you find what services would be available for your mom.

Some questions. How old is she? What does she currently use as health insurance? Is she currently getting Medicare or Medicaid?
Most likely she will qualify for a nursing home. The SSD will then go directly to the Nursing Home (I think).