If your father passed away in 2021 or earlier, your mother should start over from scratch with a new TurboTax Online account for herself. She should not try to use your father's account.
If he passed away in 2022 or 2023, and your mother did not remarry in 2022, she can still file as married filing jointly for 2022. She should use your father's existing TurboTax Online account. In the Your Info section, check the box that says your father passed away before filing this return, and enter the date of death.
