Reference: al-Muntaqaa min Fataawa Ibn Fowzaan – Volume 3, Page 168, Fatwa No.253
Question: My mother performed the Hajj with other than her mahram while she was over 60 years of age. Is her Hajj correct or should I [re-] perform the Hajj on her behalf, knowing that she has now died – may Allaah have Mercy upon her?
Response: If a woman performed the Hajj with other than her mahram, then she is disobedient [to her Lord] and has committed a sin [by doing so]. This is because the Prophet (sal-Allaahu ‘alayhi wa sallam) forbade the woman to travel without a mahram for Hajj or other than Hajj. As for the mother’s Hajj itself, then it is correct, in shaa.-Allaah. However, it is with sin and we hope Allaah forgives her [for this].