What Chinese Ethnic Minority has a courtship ritual where the couple brush their hair?

There was a video of a Chinese Ethnic Group Dance competition where a male and female represented an ethnic group where it was customary for the loving couple to show their affection and devotion to one another by combing their hair together and of the hair of the partner with small white (bone?) combs - it was very beautiful and romantic and I cannot figure out which group of the 56 official ethnic groups in China the custom belongs to.