A written statement of every payment, its amount, its payee and its refundability, and the official page reference for each. Anything the intermediary cannot point to on the official program page should not be paid.
Ask for the citation, not the reassurance
Solange should ask the intermediary to set out, in one document, each payment she is being asked to make, the exact amount, who receives it, at what stage it falls due, whether it is refundable, and where that payment is described on the official program page. A legitimate description of the program can answer all six columns. The request also does useful work on its own, because an invented step usually cannot survive being written down beside a citation.
She should keep her own copy of the official page as it stood on the day, since terms have changed. For her own household she will also want to know how many people are being counted, as each eligible joining spouse and unmarried child under twenty-one carries its own processing fee and its own gift amount.