How can a female teacher prevent feeling frustrated and feeling like a "she-devil" when she meets her students who sit with their arms crossed and do not smile, and is there any religious guidance concerning this feeling?

A Muslim should be amiable and foster amiability between himself and other Muslims, especially if he is a teacher. This is achieved by loving the believers, addressing them in the best manner, greeting them with salutations, smiling in their faces, shaking their hands, offering them gifts, and avoiding whatever repels them. This is indicated by the Almighty’s saying: (and speak to people good [words]), and His saying: (And tell My servants to say that which is best). The Prophet, peace and blessings be upon him, said: “Your smiling in the face of your brother is charity,” and “You will not enter Paradise until you believe, and you will not believe until you love one another. Spread peace among yourselves,” and “Do not belittle any good deed, even meeting your brother with a cheerful face, for that is a good deed,” and “Give gifts to each other, and you will love each other.” Umar ibn al-Khattab, may Allah be pleased with him, said: “Three things will make your brother’s affection pure for you: greeting him when you meet him, making space for him in a gathering, and calling him by the name he loves most.” The Prophet, peace and blessings be upon him, said: “Whoever wishes to be removed from the Fire and entered into Paradise, let his demise overtake him while he believes in Allah and the Last Day, and let him treat people as he would love to be treated.”