Being a U.S. citizen is a general requirement to collect Social Security Supplemental Security Income (SSI), though there are several categories of permanent residents that do qualify. They are:
There are seven categories of non–citizens who are qualified aliens. You are a "qualified alien" if the Department of Homeland Security (DHS) says you are in one of these categories:
- Lawfully admitted for Permanent Residence (LAPR) in the U.S., including "Amerasian immigrant" as defined in P.L. 100-202, with a class of admission AM-1 through AM-8;
- Granted conditional entry under Section
203(a)(7)of the Immigration and Nationality Act (INA) as in effect before April 1, 1980;
- Paroled into the U.S. under Section
212(d)(5) of the INA for a period of at least one year;
- Refugee admitted to the U.S. under Section 207 of the INA;
- Granted asylum under Section 208 of the INA;
- Deportation is being withheld under Section
243(h) of the INA as in effect before April 1, 1997, or removal is being withheld under Section
241(b)(3) of the INA;
- A “Cuban or Haitian entrant” under Section
501(e) of the Refugee Education Assistance Act of 1980 or in a status that is to be treated as a “Cuban/Haitian entrant” for SSI purposes.
In addition, you can be a “deemed qualified alien” if, under certain circumstances, you, your child, or your parent has been subjected to battery or extreme cruelty by a family member while in the United States. (from https://goo.gl/2WBcNP)
You can find more general information about SSI here: https://www.ssa.gov/ssi/
The people at the Social Security office might have been quick to reject her as they do not handle these exceptions often and probably did not ask her enough question to screen to determine if she would qualify, so it might be up to her, and her representative if she brings one, to point out the specific category of "qualified alien" she would be (if that is the case). Even if she gets an initial rejection, she can appeal where a more an administrative law judge (an actual lawyer) will more likely understand the law and be able to apply it.
I do not know her entire situation so I believe you would have to find out more from her to see if she would qualify.
I hope this answers your question. Please let me know if I can clarify anything or answer any additional questions.