The presence of a hefty Perkins loan, $2400, suggest that the aid applicant is indeed of rather limited ncome--thats part of the Perkins loan parameters--so perhaps Mom did get the FAFSA forms right.
So whats wrong with hanging back and letting Mom pay via loans that which the prevailing social formula indicate is within her ability, gap or no gap. You are free to offer assistance downstream to make qualified payments out the the 529 you have or do so for later years or even graduate school as the case may be.
Caution--places like NY and NJ tend to allow or mandate that parents continue child support thru college years while other states like PA take the opposite view ---so pay attention to the big picture if there is one. .