I contemplated just going back myself and telling her to move up, but given her mobility issue it couldn't have gone unnoticed -- she'd have had to hobble forward a dozen rows, presumably with her stuff. I thought having the FA involved might help with letting that happen after boarding calmed down. I didn't want to disrupt the boarding process through self help, as the GA and FAs were vocally focused on pushing us on time (boarding started 6 or 7 minutes late due to the gate clearing late). It's the same reason I didnt just do it anyway after the FA said no -- they were frazzled and I feared being labeled noncompliant and deboarded.

I said nothing further while on the flight, then told the ground supervisor all about it at DCA. She said she'd talk to the FA and let customer service know. I will wait 24 hours to see if I hear anything from that, and if not write it all up for them.

Still annoyed about the whole thing. Just needless and senseless. Thanks for all the feedback. I'll post an update once I hear back from UA.