The resource below is helpful, but my pensioner widow didn't live to 1907. Are there records for pre-1907 pension payments? I don't find these in the widow's pension application file.
Record Group 15 Records of the Veterans Administration, Microfilm publication M850 Veterans Administration Pension Payment Cards, 1907-1933
I can't seem to paste the pension index card here but you can see it here: https://www.fold3.com/image/5668257/sullivan-micheal-civil-war-pensions-index
This card does not list the widow's death date.