How can I help my Christian mother, who rejects my hijab and my financial assistance, while avoiding being undutiful to my parents, and is it permissible for me to take money from my husband to help my needy siblings, knowing that my father is deceased and I have no source of income of my own?

Allah has enjoined filial piety and benevolence towards parents, whether they are Muslims or disbelievers, as He says: "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," and as the Prophet, peace and blessings be upon him, said to Asma bint Abi Bakr, may Allah be pleased with her, when she asked him about maintaining ties with her polytheist mother: "Yes, maintain ties with your mother." Therefore, it is obligatory to show filial piety to your mother by visiting her and doing good deeds for her, and her avoidance of maintaining ties with you does not prevent this, because filial piety is one of the greatest acts of closeness to Allah, as long as it does not involve disobedience to Allah or associating partners with Him. It extends life and expands provision, and it is one of the greatest acts of maintaining kinship ties and showing gratitude to Allah. As for taking money from the husband to help family members, it is not permissible except with his permission and consent.