She will need to call and change her reservation, unfortunately, as she would be a "no-show" for the first segment, and hence offloaded from the continuing segment, based on the conditions of carriage:-

"when a round trip or multi-segment reservation has been made and a passenger is a no show for his or her reservation for the first segment, the Carrier will cancel the return portion or the continuing portion of the Passenger’s reservation without notification. All monies for the remaining segments are forfeited and no compensation shall be issued."

The tariff details can be found here: http://www.westjet.com/guest/en/tariffs.shtml