I do know that the story sounds confusing and blurry, so I repeat. The "Oh sorry, I didn't know that you were still eating." sentence from the psychopath mother was a lie, and which is the most important element, that - by using other, non-verbal communication forms such as gestures, etc. - she clearly, very clearly let the girl know that she was lying, and this was an abuse.
This is a very good example why psychopath abuse is so shady, under-the-table and IMPOSSIBLE TO PROVE. If the girl tells the story to anyone, nobody will understand why the girl is so mad about this. Because telling this story can not include the gesture, the intonation, the ridicule, the sarcasm, which were very very present in the live situation, but can not be quoted after. But those were the elements which gave a TOTALLY OPPOSITE meaning to the situation.
(If the girl tells the story from word to word to people who weren't there, people will think SHE is the bad one for hating her innocent mother, who even apologized for eating her food. But in reality, the real thing is the opposite.)
This is why people who grew up under a psychopath parent, tend to get mad at people for no reason. We clearly know that the "abuser" never says anything "wrong", but we still get abused as fuck. So when we get to the real life (where there are no psychopaths present), we still tend to interpret totally innocent words as hidden attacks.
This, later, will lead to TOTALLY INAPPROPRIATE, and "anti-personality" emotional reactions, which can eventually confuse you about who you are. You will get mad at people who you know you shouldn't be mad at, and will accuse people on things you know they'd never do.