Please accept my condolences; I faced the same challenge 10 years ago.
The responsibility for filing the Income Tax Return of a deceased person depends on how that person filed in the previous Tax Year. If she filed a Joint 2021 Tax Return, assumably with her spouse and the spouse survives her, then the spouse must file a Joint 2022 Tax Return listing your mother as having deceased in 2022. If your mother was a widow, then the responsibility for filing her 2022 Tax Return rests with the Executor of her Will or her Estate. It's rather easy, straight-forward, and uncomplicated; if your mother was "elderly" it might result in a refundable credit.
