The young woman celebrating her fifteenth birthday is traditionally called a quinceañera in Spanish.
The term is feminine and is closely related to quince, the Spanish word for 15. In everyday usage, quinceañera can refer to both the honoree and the celebration, so context determines which meaning is intended. English writing often keeps the Spanish word rather than translating it.
The event is associated especially with Latin American and Latino communities, but its customs are not identical everywhere. Families may adapt the celebration to local traditions, religion, personal preferences, and available resources. Some quinceañeras include a formal court, choreographed dances, and a large reception; others are much simpler.
The word should not be confused with madrina, which means a female sponsor or godmother, or dama, which commonly refers to a female member of the court. Those people may have roles in the event, but neither term names the honoree herself.