What is the ruling regarding a widow remaining alone in a rented house far from her family, while she is fearful and unable to pay the rent?

A woman observing the 'iddah (waiting period) due to her husband's death must remain in the house where her husband passed away, as the Prophet, peace and blessings be upon him, commanded Furay'ah bint Malik to do so. This is the view of the majority of scholars, though they permitted the woman to move if she feared for herself, or if she could not find someone to attend to her needs, or if it became impossible to reside in her home for any reason. If the situation is as you described, with the woman fearing for herself or being unable to pay the rent, then it is permissible for her to move to her family's house to complete her 'iddah there.