Book the seat on the 24th and a return for the first open Aeroplan seat on the 25th or 26th. Have her go out to the airport after grad to standby for whatever opens up on the later flights. On an Aeroplan ticket, one can stand by for any flight on any day. If there are no regular open seats, she won't be boarded, but when the flight closes, if there are any open seats, she'll get one, even on an Aeroplan ticket. I have stood by twice in the past few months using an Aeroplan ticket and got on the earlier flights. Granted I am Elite, but once the flight is turned over to the gate, there is no difference between a paid seat and an Aeroplan seat. There will be a priority to getting any open seats based on status and fare paid, but she should get on unless all flights are 100% sold out. By the way, have you been trying J and Y class?