I am so going to do this too!
Passengers are always more likely to complain to airlines, however we should also show and express our appreciation when a flight attendant deserves it, and Ms. Nina definitely does.

One more thing, about the white table cloths in European C class, on WAW-BER there wasn't any, just a tray.
Today BER-WAW there were table cloths, and I asked why sometimes the tray is on the cloth and sometimes it isn't.
Ms. Nina told me that it depends on whether the table cloths are loaded on board or not. Apparently, LOT doesn't load them now on every flight.