IMHO:
There is no "sure" way for you now since you siad you don't have miles for upgrade.
but:
1. arrive to the gate early and ask the gate agent nicely.
2. try fly on a 777 exit row so even you don't have UG you still get the best seat in coach.
3. But in terms of "inspiring" your GF, find a time to check-in that you know many people will be checking-in, instead of going through the 30mins queue, walk up the the less than 5mins Buz line. This is already impressive.
Good Luck