What is the girl celebrating her 15th birthday commonly called?

The girl celebrating her 15th birthday is commonly called the quinceañera.

The term comes from Spanish and is the feminine form associated with quince años, meaning “fifteen years.” In everyday usage, quinceañera can identify both the celebrant and the birthday celebration, so context determines which meaning is intended.

The word is widely used in Mexico, Latin America, and Latino communities in the United States. Spelling and pronunciation can vary in informal English, but the Spanish ñ is part of the standard form. A boy’s comparable celebration is sometimes called a quinceañero, although practices and terminology are less standardized.

The quinceañera is usually the central participant in the ceremony and reception. She may be accompanied by parents, godparents, attendants, relatives, and a court of honor, depending on local and family tradition.