Is it permissible to appoint someone to perform Umrah on behalf of a woman who cannot travel to perform it herself due to the unavailability of a mahram for her, despite her financial and physical ability?

For the代理 (niyabah - deputizing/performing on behalf of someone else) in Umrah (definition) on behalf of a living person to be valid, it is stipulated that the person must be incapacitated by an inability that is not expected to cease, and that they authorize the代理. It is also stipulated that the person performing on their behalf must have already performed Umrah for themselves. Therefore, the代理 for the aforementioned lady in Umrah or Hajj is not valid.