Does the guardianship of the guardian appointed by the sister to solemnize her marriage contract cease immediately upon the completion of the contract, or does his guardianship continue to include following up on her affairs and resolving her marital disputes and what ensues from that, and is he accountable for her before Allah and the sister?

The guardian (wali) is one of the pillars of marriage (nikah), and marriage is not valid without him, based on the Prophet’s (peace be upon him) saying: "There is no marriage except with a guardian," and his saying: "Any woman who marries without the permission of her guardian, her marriage is invalid." A woman does not have the choice of guardian, for guardianship is a legally established rank, and her closest guardian has the most right to marry her off, unless his guardianship is forfeited by a legitimate cause. If a woman has no guardian and no ruler, she may appoint a trustworthy Muslim to marry her off with her permission. If she wishes to marry again and there is no guardian, she may appoint another trustworthy person.