Originally Posted by sbiddle

Air NZ only allow mix and match fares online between the different S2S offerings (ie 1 pax seat only 1 pax the works) but the call centre can do a mix and match fare with a BP or PE and a economy S2S fare basis.

Yes they'll no doubt charge a booking fee but it will allow both people to be on the same PNR and for the upgrade to clear immediately assuming she is your elite partner.