My Mum (90) didn't follow-up on a financial matter when she said she did. Should I let it go or remind her?

Mother is very lucid about the distant past and has a great sense of humor in general. However, as I work daily, I leave it to her to follow up on an overdrawn account letter from her bank or a needed letter that only she can request from her teacher's retirement agency at the state level. I was there once when they called and gave her a number and extension to call, only because I took that day off from work and happened by the phone when it rang and she picked up. She assured me the next day that she had calle dand requested the document needed so we can qualify her for a Home Attendant. It troubled me in my sleep a few nights later, so I called the agency from work the next day, only to find out the document has NOT been requested for this year 2015, as I instructed Mum to do. Should I throw it in her face and remind her that she did not do as required, or say nothing. Nothing short term seems to "stick" anymore for more than a few seconds. "Help Me" (Joni Mitchell)