Okay, so there's good news and there's bad news.
The bad news first:
At the moment (February 2019) all New York State adoptees' Original Birth Certificates (OBC's), and usually their adoption paperwork as well, are sealed. Totally sealed. Doesn't matter if the adoptees are dead, doesn't matter if they're alive and they already know all the info on the original paperwork and they have already reunited with their biological parents. The paternalistic and restrictive law remains on the books. They are denied their own records.
And now for the good news:
Luckily, attitudes towards adoptee rights are changing across the country, and New York is no exception. There's a new bill that was just introduced in the New York State Legislature, with many co-sponsors and solid bipartisan support, that would allow any New York adult adoptee to regain access to their paperwork! Check out the New York Adoptee Rights Coalition (NYARC) for details about the bill, and sign up for their e-mail newsletter for updates: http://nyadopteerights.org/
The bill also includes provisions for direct-line descendants of deceased adoptees to gain their OBC's: children, grandchildren, etc.
So if this bill passes this session, you should be able to get a copy of your grandmother's paperwork from the state on January 15, 2020.