The formal group of attendants accompanying a quinceañera is called her court of honor.
A court of honor commonly includes young women and young men selected by the celebrant. Members may participate in the entrance, formal photographs, choreographed dances, and other public parts of the celebration.
The court resembles a ceremonial escort group, but it is not the same as a wedding party. Its composition, size, and roles vary considerably, and many modern celebrations use a smaller court or omit one entirely.
Spanish terminology for individual members differs by region and gender. Because those terms can vary, “court of honor” is the clearest general English label for the group as a whole.