What is the ruling on a wife spending the night at the house of her friend who has an unmarried brother, and does the religious upbringing of the friend's family affect the permissibility of this, such as her parents not praying or not adhering to the rituals of Islam?

A woman staying overnight at her friend's house is permissible under certain conditions: being safe from temptation, the absence of suspicion, no private seclusion with a non-mahram man, and that it does not lead to something forbidden, such as disobeying her husband. If the people of the house are negligent in religious observances, especially those who abandon prayer, their side is generally not trustworthy. As for the Udhiyah (sacrifice), it is a confirmed Sunnah for the able, according to the majority of scholars.