She was a little wacked, not cashing the checks. She could have kept books on the checks vs. the total she was owed and still pursued her case.
She might not have been able to understand how SS could pay her piecemeal, but again money is money and an account is an account. It’s not like, if this came to a court, the court would have required her to pay back $X to get $X + $Y.
THIS is probably the thing that got her sent to the shrinks.