Should my sister-in-law give a red envelope for her birthday?

should be Sister-in-law is her husband's sister and an important factor in her relationship with her mother-in-law. Good relationship with sister-in-law is also the key to promote the harmonious relationship between mother-in-law and daughter-in-law. Sister-in-law should give her a red envelope on her birthday, not only because she is younger than you, but also to promote the further development of their relationship.