As part of labor negotiations it may be written into the FA's contract that on flights over a certain distance the FA receives a BusinessElite meal. The bigger question is why the FA had to eat it right in front of paying pax, but it could very well be that there are insufficent jump seats that are cordened off and another crew member refused to give up a seat so the FA could eat (I am not saying that that was what happned just that it was a possibility)