In fact, you have to understand that you have no responsibility and obligation to educate and guide your brother. This is your parents' responsibility. You just have a greater influence on him, so in the face of mother's denial, criticism and disgust, all you can do is try to speak out your true feelings and needs bravely and sincerely at that moment, so that she can clearly realize that her words and deeds have deeply hurt you.
It is never your responsibility to educate your brother. Keep this firmly in your mind and practice it in your actions and words. As a sister, your words and deeds will certainly affect your younger brother, but it is also his own choice for his younger brother to choose to accept those words and deeds to learn. The person responsible for his bad habits is himself. Return the troubles that don't belong to you to others and allow them to live according to their own wishes. You need to pay attention to yourself.
The reason why a mother accuses, denies, criticizes and hates you in the face of her brother's bad habits may be that she feels powerless and helpless in the face of her brother's bad habits through you, or it may be that this part of her emotions are directed at her father, eager to get his strong support and help, but unwilling to admit her vulnerability in front of him and need his support and help. This is the part that needs her to feel and grow. What did you say?/Sorry?
Be yourself at ordinary times, have a certain degree of self-discipline, set an example, impress my brother and be willing to change. After all, if my brother removes these things, family relations will be more harmonious! By writing an emotional diary, you can record your painful emotional feelings caused by your mother's criticism, negation and severe criticism in words, which will help you better perceive and sort out your emotions, so that your emotions can be well seen, expressed and released.