In her past live, she was raised by that head maid who underfed her with bland food and taught her anything she does is wrong on the empress's orders. She was brainwashed into thinking up is down. Considering her resulting deep insecurities and how her public image was destroyed little by little over the years with her death as a result, anything bad seems like a major mistake to her. Much like how a person or animal subjected to abuse will shy away in fear or become anxious if you make a sudden movement, raise your hand, seem displeased or are in a bad mood. Not finishing your meal is not an issue unless for years you've been told you're a failure, a disgrace and how everything you do is bad and everything bad is your fault.