Is it permissible for a woman whose husband has died to leave her home out of necessity?

It is permissible for a woman observing the 'iddah (waiting period) for widowhood to leave her home during the day to attend to her needs and necessities, such as medical treatment or completing government procedures, if there is no one to act on her behalf. However, she should not go out at night except for a necessity, because the night is a time prone to corruption, unlike the day. She must spend the night in her home and not elsewhere.