Would a daughter be considered disobedient to her father who abandoned her and her brother from a young age, does not respond to her attempts to communicate with him, and accuses her of disobedience and ulterior motives despite her need for him as a guardian?

It is common for a father to love his children and strive for their well-being. However, the father's actions mentioned, such as abandonment, disowning, and failure to provide, are reprehensible and incur sin, as the Prophet (peace be upon him) said: "It is enough sin for a man to neglect those whom he is obliged to support." A father is obligated to provide for his daughter until she marries, and for his son until he reaches maturity. Some jurists have even mandated support for an adult who is poor.

No matter how negligent a father may be, this does not absolve his children from honoring him. Honoring one's parents is commanded even if they strive to make the child commit disbelief, as in the verse: "But if they endeavor to make you associate with Me that of which you have no knowledge, do not obey them, but accompany them in [this] world with appropriate kindness." It was narrated from Ibn Abbas (may Allah be pleased with them both): "There is no Muslim who has two Muslim parents, and he wakes up to them seeking Allah's reward, except that Allah opens for him two doors [meaning: of Paradise] – and if he has one, then one. And if he angers one of them, Allah will not be pleased with him until he is pleased with him." It was asked: "Even if they wronged him?" He replied: "Even if they wronged him."

You have done well in your efforts to communicate with him. We advise you to supplicate for him frequently, try to involve righteous people to mediate a reconciliation, and seek the reasons for his anger to resolve them. If he continues to shun you and you have not been negligent towards him, then it will not be considered disobedience.