Quinceañera can mean both the girl celebrating and the celebration honoring her 15th birthday.
In Spanish usage, the word most directly refers to the female celebrant. In English and in widespread popular usage, it also commonly names the party or tradition itself. Context usually makes clear whether someone means the person, the event, or both together.
The term is formed from quince, meaning 15, and the feminine noun-forming ending associated with a young woman or female person. The ñ is pronounced with the palatal sound heard in Spanish words such as año.
Quinceañera should not be confused with madrina, which means godmother or sponsor, dama, which can mean a female attendant, or chambelana, a feminine form used in some communities for an attendant. Those words describe people connected with the celebration, not the central celebrant or event.