What is the ruling on the relationship with a sister who has deeply hurt the questioner with her words and actions, and the questioner is certain that the sister does not love her, while the questioner maintains ties with her but harbors no affection or love for her?

Maintaining kinship ties is obligatory, and it means connecting with relatives even if they cut you off, not merely reciprocating those who connect with you. A Muslim should seek reward in connecting with those who have severed ties with them, and Allah will be their helper. As for love, a Muslim is not obliged to love someone who wrongs them, but there must remain a love for the sake of Allah, and the firmest bond of faith is love for the sake of Allah and hatred for the sake of Allah. A Muslim is loved in proportion to their faith and disliked in proportion to their sins.