If there are no other expenses to be taken into account, or other 1099Q Forms from other 529 plans for the student/dependent, I believe Mom is stuck.

The moral of the story is NEVER pay for school and then get reimbursed if the owner and student are not the same person.  Have the money go directly to the school to pay qualifying costs.

You don't mention the specifics of the student/dependent's tax situation but it is possible because of the kiddie tax that the amount due will be close to or the same on either return.