Your mother has to file her tax return with the name that is on her Social Security account. If she never changed her name with Social Security, she has to keep using her maiden name on her tax return.
If she wants to change her name with Social Security now, don't try to coordinate it with filing her 2021 tax return. File the 2021 tax return with her maiden name, wait until it has been processed and she gets her refund, then change her name with Social Security.
