Is it permissible for a woman to travel for Hajj with a campaign without a mahram if her only mahram is unable to travel with her?

Hajj is not obligatory for a woman unless she is able, and the presence of a mahram (definition) is a condition for ability. If a mahram is not available to her, then she is not legally able, and there is no sin upon her. It is not permissible for her to go for Hajj without a mahram, based on what was narrated from Ibn Abbas, may Allah be pleased with both of them, that the Prophet, peace and blessings be upon him, said: "A woman should not travel except with a mahram."