Moving Elderly Mother from Arizona to New Mexico, SSI eligibility

My mother is currently living in Arizona and is End State Renal Disease (ESRD) requiring dialysis three times a week. The cost of dialysis is currently covered by Arizona Medicaid and Medicare. Due to declining health, we need to move her to New Mexico; to be closer to family care. She is receiving $750/month in Social Security widower benefits. According to NM Medicaid rules, the $750/month makes her ineligible for NM Medicaid. With the 80% Medicare coverage, the 20% out of pocket cost for dialysis would be approximately $5,000 per month, which my Mother cannot afford. Her SS monthly payment of $750 is her sole source of income, and she has total assets less than $1,500.

NM does use SSI eligibility as a qualification for Medicaid. Can my Mother forfeit her SS widower benefits, and apply for SSI instead? The difference in the benefit of $60, far off-sets the cost of her dialysis, if she can't qualify for NM Medicaid.