Must I speak to my daughter who has not spoken to me for over two months because of her feeling of inferiority towards her brother and her accusation that I favor her brother?

The mother should talk to her daughter and advise her to persuade her to return to her studies, explaining that failure is a temporary setback that can be overcome through diligence and seeking help from Allah. There must be justice among children, as the Prophet (peace be upon him) said: "Fear Allah and be just among your children." The brother should advise his sister and comfort her.

The daughter mentioned is in great danger due to her disobedience to her mother and the obligation to honor one's parents, as Allah Almighty says: "And We have enjoined upon man, concerning his parents, good treatment" and "And accompany them in [this] world with appropriate kindness." One form of disobedience is her abandoning her mother and brother. The Prophet (peace be upon him) said: "It is not permissible for a Muslim to abandon his brother for more than three nights." Among her transgressions is her envy of her brother's excellence. Therefore, she must hasten to repent before it is too late.