Some airlines (like CX) detail the "fare calculation" on the eTicket, but very few do. AF does not.
You only have the total return fare and the details of all surcharges and taxes.
When you initially booked, you might have separate screens for the outbound and inbound, but not on the final ticket. The outbound could be more expensive than the inbound or vice versa.
You have to trust AF for the calculation.
If she voluntarily cancelled the flight, although it might operate, she should be happy to get a good refund, even in the form of a voucher.