Is it permissible for a female student who benefits from her companion's salary to continue receiving his salary, after he has returned to his country, in order to cover rent and help her other brother, with the companion's knowledge and consent?

The stipend is due to the accompanying محرم. If he cuts short his companionship and returns, he is not entitled to it except with the permission and consent of the granting authority. One must refer to the authority that pays the stipend and inform it of what happened, to determine the fate of the stipend. It is not permissible to dispose of the stipend before consulting the granting authority and understanding its conditions and how to dispose of it when the accompanying person returns and severs his connection, based on the Almighty’s saying: (O you who have believed, fulfill [all] contracts) and the Prophet’s (peace be upon him) saying: (Muslims are bound by their conditions).