The RMD required to be taken for 2021 is her dad's RMD. Any portion of her dad's 2021 RMD that her dad had not taken as of his death in April 2021 must be satisfied by the beneficiaries and can be taken by the beneficiaries in any combination.
The SECURE Act only affects the beneficiary RMDs which under the proposed regulations are to be taken annually based on the Single Life Expectancy of the beneficiary in 2022, reduced by one each subsequent year and the entire inherited IRA must distributed by the end of 2031.
