I'm flying BOS-CLT-SFO in the near future, and someone I work with (no status) will be doing the same. However, she may be returning to BOS sooner than I am. If we fly BOS-CLT-SFO together but not the return, is she eligible for a companion upgrade on the outbound? Or does she have to fly the entire itinerary to be eligible for the upgrades? Thanks!

Absolutely.

I regularly 'companion upgrade' a friend for only one of her two outbound legs.

I think I'm correct in saying that you can only upgrade a companion who is travelling on the segment(s) you are on. Therefore, you can upgrade her on your outbound since you are together. But not on the return since you're not together.

As stated above, your companion is eligible for an upgrade when you are travelling together on that flight. Many people upgrade military personnel (or attractive total strangers ;) ) for a segment irrespective of the rest of the itinerary.

Thanks to the wonderful CP angels, I've had a companion upgraded when he was seperated from me because of irregular ops, but I wouldn't bet on it.

Yes, Companions can upgrade on all segments that you both fly on!

I'm flying BOS-CLT-SFO in the near future, and someone I work with (no status) will be doing the same. However, she may be returning to BOS sooner than I am. If we fly BOS-CLT-SFO together but not the return, is she eligible for a companion upgrade on the outbound? Or does she have to fly the entire itinerary to be eligible for the upgrades? Thanks!