Required Minimum Distribution Reporting for Pension Plan Beneficiaries

I am helping a friend with her taxes. She inherited a pension from her deceased spouse many years ago and has received a 1099-R. TurboTax is asking whether any of the money she received from the pension in 2021 is a required minimum distribution and, if so, how much. What are the reporting rules on this? She is in her nineties. Thank you for your help.