Is it sufficient to greet one's father's wife when visiting her for the sake of kinship, given the existing aversion towards her due to her leaving the home after the father's death and what resulted from that, and is it considered a sin to distance oneself from her and not visit her?

As long as you do not abandon your stepmother or mistreat her, there is no sin upon you. However, it is an act of filial piety towards your father to maintain ties with his wife and honor her, as the Messenger of Allah (peace and be upon him) said: "The most dutiful of deeds is for a child to maintain ties with the loved ones of his father." You do not have the right to hold her responsible for what happened to your sister. You should busy yourself with matters that benefit you and your sister, both in religious and worldly affairs.