As someone alluded to earlier, you have very limited options for upgrades if you are Silver on CO, particlularly traveling to/from/connecting to hub cities as Houston, Newark, etc. so you may not have that many opportunities to get into a fight with your GF over the upgrades anyway.

Secondly, I suppose I understand where your GF is coming from. My ASSUMPTION is that she believes that by opting to upgrade yourself rather than her, it indicates that you are less concerned about her comfort (well-being) and more concerned with yours--which would translate to your being selfish in her eyes.

What the heck, be a gentleman and give her the darn seat. Who knows, she may reward you.