Welcome to Flyertalk and to the British Airways board, SteveMac. It's good that Google brought you to us, I hope you are enjoying the feast of information here and that you will continue to participate.

Firstly I'm surprised she noticed, and slightly surprised she commented on it. It may be she also works on the so-called "lo J" 747 fleet where there is an issue of WTP cabin being in the wrong place, and your actions may have confused her. Alternatively she may have thought the WTP passengers may have thought you were WT and she was therefore trying to persuade you to stick to your cabin.

I don't think you did anything massively wrong, and maybe she over-reacted slightly (a light hearted joke may have been a better way to handle it on both sides). I doubt it will ever happen to you again.