I was thinking of buying my girlfriend an upgrade as she hates the increasingly small cattle cages in the back for long-haul flights
So you normally ride up front and your girlfriend has a ticket down the back ?
As Dash8driver1312 said. Contact the company and put in a SPML request for both you and your girlfriend. Job done.
Quite frankly, I wouldn't touch seafood on an airline anyway, allergy or not...