Is the questioner to be blamed for not accepting her biological father as a father, given that her grandfather was the one who raised and cared for her after her parents' separation and her father's refusal to provide for her?

A father's neglect of his daughter and his failure to provide for her is an act of injustice and sin. However, this does not change the reality of his fatherhood, his responsibility towards her, and his rights over her. A grandfather's kindness does not elevate him to the status of a direct father, nor does a daughter's rejection of her father nullify his rights over her. Therefore, the daughter must honor her father, and abandoning him is a grave act of disobedience. Whatever estrangement she may feel towards him, it is not permissible for that to prevent her from honoring him and fulfilling his rights. Among the things that help in honoring one's father are striving against one's own desires, seeking help from Allah, purifying one's intention, and remembering the virtue of honoring one's parents. It is among the greatest causes for Allah's pleasure and entry into Paradise. The Prophet, peace and blessings be upon him, said: "The pleasure of the Lord is in the pleasure of the parent, and the wrath of the Lord is in the wrath of the parent."