What should a female questioner do who regrets not having scheduled a visit to her maternal uncle before his death?

There is no sin upon you, apparently, as there is nothing that necessitates it, unless you intended to break ties, in which case the sin would be due to this intention; because the Prophet, peace and blessings be upon him, said: "Actions are by intentions." Fulfilling a promise is recommended by the majority of scholars, and you did not specify a particular time to inform him.