Dear Ms. Clark,
Thank you for posting your request on History Hub!
In most cases, the National Archives will not have a copy of her certificate of citizenship. Two copies of the certificate were created – one given to the petitioner as proof of citizenship, and one forwarded to the Immigration and Naturalization Service (INS). All INS records are now overseen by the US Citizenship and Immigration Services (USCIS). We suggest that you submit a Freedom of Information Act (FOIA) request to USCIS to obtain a copy of your mother’s Alien Files (A-Files).
We hope this is helpful. Best of luck with your family research!