Is my mother considered sinful for refusing my marriage to the person I desire, while conditioning her approval on my marriage to my paternal cousin, whom I do not want?

A Muslim girl must choose a man who possesses both religiosity and good character when getting married, and strive to convince her mother of him, for obedience to parents, dutifulness to them, and showing kindness to them are religious obligations. If the mother insists on refusal, and the man is pleasing in his religiosity and character, while her paternal cousins are not competent in religiosity and character, then her obedience is not mandatory, and it is permissible to marry him without her approval. The father is the guardian in marriage, and if he is not present, then the closest male relative from the ‘asabah (agnates).