The earliest you can put a companion on the list is two hours at the airport. I did put a companion on the list (in PC) last month a day in advance and she got the upgrade SFO to SAT via IAH overnight for one flight and at the airport for the other.

Make sure to seperate the PNRs as stated. I would suggust just buying the tickets seperate as it allows each of yall to get the 500 mile bonus and the $5 credit for booking if you have the travel account.

I havent seen in any of my double bookings were you save any money by booking together rather than seperate. Good luck with the upgrade.