Who should the red envelope given by the sister-in-law to her mother-in-law belong to?

The red envelopes given by brother-in-law to mother-in-law are generally mother-in-law's. In China culture, the mother-in-law is regarded as the elder and the main manager of the family, while the brother-in-law is married into the family as the daughter of the mother-in-law. Therefore, the red envelope given by my brother-in-law to my mother-in-law is a sign of respect and filial piety, aiming to show my respect and gratitude to my mother-in-law.