What is the ruling on a wife abstaining from all foods and activities that her deceased husband used to love, and what is her religious obligation?

Scholars differ on the consequences of prohibiting what is lawful. The most preponderant opinion is that expiation (kaffarah) is obligatory, because Allah called this prohibition an oath (yamin), as He Almighty said: "O Prophet, why do you prohibit what Allah has made lawful for you, seeking to please your wives? And Allah is Forgiving and Merciful. Allah has already ordained for you the dissolution of your oaths." So, the woman must return to consuming the foods and performing the permissible actions that she prohibited for herself, and she should know that this is not part of Allah's law. The expiation for an oath is feeding ten needy persons, or clothing them, or freeing a slave. If she cannot find any of these, then it is fasting for three days. As for a woman whose husband has passed away, she must observe 'iddah mourning for the duration of her waiting period.