Frederick's mother is clearly at her wit's end about how to encourage her son to stop crying. The text tells us that she has tried withdrawing privileges when he does cry, such as going to the zoo for example, however what infuriates her is that Frederick appears not to care at all if he is punished for crying and has something taken away from him. He just carries on. She rarely openly castigates him, but the constant nagging and belittling is something that seems to be a key feature of her speech with Frederick. She tells him that if he carries on like this he will not settle well into school, for example. Finally, driven to distraction by the way that he responds when she tells him as punishment for crying he will not go to the zoo, she says to him she is glad that his father is no longer here to see him act like this because he would be so ashamed. Note what she does then, telling her son to control himself before going on:
She walked fast, the gap between her and Frederick widened.
We can see that this is the action of a woman who is very unsure of how to try and get her son to stop crying, but also it is the action of a woman who is so emotionally disengaged herself that she is unable to witness her son's tears for long. The further she gets away from her son, the calmer she becomes.