Here's two somewhat similar experiences. My wife and I were flying paid C on BMI TATL and she spilled her own drink into her seat. Immediately an FA detached the seat cushion and snapped in a spare dry one. Now that's service.
Recently my wife and I were flying 80000 mile roundtrip US award tickets on LH TATL. The seating was 2+2+2 and we had a window set. Before we took off I played with my seat controls and the seat wouldn't go back to perfectly upright. I told the FA it wasn't a problem. But it was a problem in their minds for take off and landing. There was one empty C seat in the center row and the FA told me that the gentlemen next to the empty seat in the center row had agreed to take my wife's window seat so wife and I could sit together. I politely said we both enjoyed the window view. So they moved me to an empty window seat in First for the take off and landing and gave me one premium drink in F (Johnnie Walker Blue Label Scotch). I thought they handled that with class and decided not to aggravate myself by trying to get both of us moved to First for the whole flight. I figured that the full F upgrade wasn't worth a try since business was packed but there were only 2 pax in 8 seats in F; it didn't seem like F was easy to get as a freebie.
But UA doesn't guard its C seats like LH appears to guard its F seats. UA should have moved her up to an empty C.