Sister and brother-in-law get married, and I will send roses as my brother, okay?
Sending flowers is a wise choice. Girls like flowers, what they want is that romantic feeling. Now that they are married, send her a bunch of 99 roses, representing eternity. Sister can send a bunch of 99 pink roses to the wedding, which is fashionable and romantic, or 16 red roses with 2 lilies, 16 stands for constant love, and 2 lilies stand for centuries of harmony.