Is the wife obligated to serve her husband's mother with such mentioned devotion, and is that considered a religious duty?

Among the effects of the marriage contract is the wife's obligation to allow her husband to enjoy her in return for his financial support. She is not obligated to serve her husband's family unless she volunteers to do so. The husband should not ask her for anything that is not legally binding on her. We advise the wife to strive to end the dispute with her husband's mother, as this brings happiness. The husband must also fear Allah concerning his wife and not link his relationship with her to her relationship with his family. He should strive to reconcile them, utilizing his relationship with both parties to unite them in love.