No, the distributions are not subject to 10% withholding if the beneficiary (even if an estate) elects out of it.  So at least now we know the daughter created this mess.  Is she your client?  I wouldn't want to be doing returns for both the widow and the daughter, because they have a conflict of interest and I would have to explain to both, the harm they had caused.  

If the widow is your client, the IRA has nothing to do with her 2021 return. If the daughter is your client, did she even request an extension for the 1041?  Was there any reason for her to keep the money from her mother?  I am not trying to imply there is something shady.  Just stupid.