Reference: Fataawa al-Hajj wal-‘Umrah – Page 11
Question: Some women from Makkah travel to perform the hajj without their mahram, going in groups of women on public transport. So is this permissible?
Response: That which is correct is that it is not permissible for a woman to perform the hajj without her mahram. Even if she was from the [resident] people of Makkah. That is because the distance between Makkah and ‘Arafah is considered a journey according to the preponderant opinion [of the scholars], and this being the case, the people of Makkah would shorten their prayers along with the Prophet (sal-Allaahu ‘alayhi wa sallam) throughout [their time at] the places of the sacred rites.