The payments and withholdings for the seven months she was alive go on her final 1040.  The five months of erroneous income go on the estate's 1041.  The estate can use a fiscal year, and should try to get the money paid back by June.  Add it in, then subtract it out.  Even if it's not paid back yet, you can use accrual method.  Attach explanations to both returns.  Don't expect quick processing.