I agree with ESOP Guy, once you have a required beginning date, there is nothing that would allow you to stop or suspend RMDs merely because you were re-hired. Even though the RMD due 4/1/2021 was waived, it still counts as the RBD and RMDs would be required for 2021 and every year thereafter.
The question becomes, is 2020 really a distribution calendar year? As CuseFan pointed out, if she terminated in 2020, it could only be a distribution calendar year if her date of birth was on or before 6/30/1949; otherwise her first distribution calendar year would be the later of when she turns 72, or retires.
There is, unfortunately, no definition of "retires" in the regulations. If she was born on or before 6/30/1949 but, at the end of 2020, the employer reasonably expected her to return to work in a couple of months' time, I think you could argue that she did not retire, and therefore it would not trigger a RBD. This is not a terribly aggressive position in my opinion, but there is no official support for this stance either. If you want to play it on the safe side, have the employee take the distributions regardless.