Is a niece obligated to visit her paternal uncle as a duty of maintaining kinship ties, and what should she do if her husband prevents her from doing so, and is it permissible for the uncle to reciprocate her action if she does not visit him?

You must continue to maintain kinship ties with your niece, even if she does not visit you, because the Prophet, peace and blessings be upon him, said: "The one who maintains ties is not the one who reciprocates, but the one who maintains ties is he who, when his kinship ties are cut, he reconnects them." If her husband prevents her from visiting you, she must obey him, because obedience to him takes precedence over maintaining kinship ties, in order to avoid corruption.