Hi everyone and Merry Christmas!!!

I'm an AA/UA guy normally so seeking the boards' opinion on what to do about a (very 'first world') travel issue...

Coming back from holidays next weekend, and it turns out I'm on the same flight as the girlfriend (she was originally flying back later, but work calls). I've got a paid F ticket (A booking code) from the holiday sale, and she has a paid J class (I), also from the sale.

Flight is LHR-JFK, currently showing F9 A8 J9 C2 D1 W6 Y5 B5 H0 K0 M0 G0 w/ no reward availability in any cabin.

Unfortunately, trying to upgrade w cash tries to re-price into full F or something similar ($5XXX!), so I was wondering if the board's collective wisdom had any brilliant ideas? I've got Avios, and would be willing to pay something reasonable (in the 1k range) for the upgrade.

Other than trying for an AUP at the airport, any advice? Or is whoever would have had the seat next to her in J getting a very nice free upgrade to my seat!

Thanks in advance
747