I'm going on a cheap trip to Miami with my girlfriend on HP. She's Silver, I'm Gold. My FC upgrade's already set on the main segment, she has to wait till day of flight. It's a 757, but there are only 4 seats left. If for whatever reason she doesn't get one of them, she'll have no options to upgrade using miles and one of us will be sitting in coach.

Can she buy "insurance" by using miles to upgrade now, then return the upgrade if there turn out to be seats available in F (for an op up) once the Silver window opens?

I'm finding coordinating upgrades for travel companions of different status levels can be quite problematic.