What is the ruling on shunning a sister who has been described as selfish and who caused a婚約破棄 (faskh al-khutubah - annulment of engagement), knowing that she meets attempts at reconciliation with aversion, and what is the ruling on hating men and refusing marriage because of this experience?

Alienating a suitor from his fiancée is forbidden in Islamic law. Your sister must repent if she has done so. However, you should verify the matter, as she might be innocent.

You should forgive your sister and forget what happened, for perhaps Allah willed good for you by diverting this suitor away from you.

Boycotting and abandoning your sister is forbidden in Islamic law. It is not permissible for a Muslim to abandon his brother for more than three nights. Rather, you should treat her kindly, even if she has wronged you.

Do not refuse those who propose to you if they are of good character and religious devotion, for the Prophet, peace and blessings be upon him, said: "If there comes to you one whose religious commitment and character you approve of, then marry him. If you do not do so, there will be turmoil on earth and widespread corruption."

As for the first suitor who proposed to your sister, it is better to leave him and turn away from him due to the family's opposition and his previous behavior, which could cause disagreement and discord.