@mkschmidtjr
Because of her age, she isn't gonna qualify for an ACA plan (Healthcare.gov) or any private insurance.
But it sounds like she can do a BUY IN to Medicare Part A and from that point she can buy into Part B. She can either buy a Part D Rx plan or if she can get a Medicare Advantage plan some come with Part D attached.
I can't figure out why Social Security didn't mentioned this to her years ago.
AARP: How do I qualify for Medicare?
SHE HAS TO PAY FOR MEDICARE PART A AND PART B
Medicare.gov - Medicare Cost At A Glance
Below is a Medicare.gov worksheet that does not get into specifics but will tell you if she is eligible and what her premiums will be - just follow along & answer - the citizenship question does not come until the end.
Medicare.gov - Eligibility & Premium Calculator
I am just gonna give you my Medicare "Search" page link so you can read anything else that might apply to her or do another search for something specific - I search for "Immigrant eligibility"
.https://www.medicare.gov/search/medicare?keys=Immigrant+eligibility
A GOOD LOCAL MEDICARE Insurance Broker that knows all the ins and outs of Medicare maybe beneficial to you here -make sure they are knowledgeable on this topic.
My pal, somarco might be able to give you more info about using this type of professional. I am sure he will be available shortly.
It isn't cheap but better than what you quoted - a rough guess would be about $ 625 per month for everything Part A, Part B, Part D - I do not know if they will assess her a penalty for not signing up when 1st she could - I think not.
I do not know if there is any extra help for her if she is very low inome - maybe.
Let us know how it goes.
It's Always Something . . . . Roseanna Roseannadanna