http://www.aircanada.com/en/aeroplan...des/howto.html

Travel using another member's eUpgrade credits

Currently, only one member may sponsor an upgrade per reservation. For instance, if a Super Elite and Prestige member are travelling together on the same booking, it is not possible for the Super Elite member to sponsor an upgrade for the departing flight(s), and for the Prestige member to sponsor an upgrade for the return flight(s).


Meaning you are using your eupgrade credits to upgrade your inbound legs, which is fine however your wife is trying to upgrade you on your outbound legs, which will not work because you can only have one member sponsoring per reservation/itinerary.