The traditional Spanish term for the girl who celebrates a quinceañera is quinceañera.
The same word commonly names the celebration itself and its female honoree. In Spanish, the feminine ending distinguishes the term from quinceañero, which can refer to a boy celebrating a comparable fifteenth-birthday milestone. English usage often uses quinceañera for the entire event as well as for the celebrant.
The word is tied to quince, meaning fifteen. That connection explains why the celebration traditionally takes place at age 15 and why quince años is another common name for it. The event’s exact customs, however, are not identical everywhere.
Terms such as dama and madrina describe other possible participants or roles in some celebrations, not the central celebrant. A quinceañera may have attendants, sponsors, relatives, or friends, but those titles do not replace the name for the girl whose fifteenth birthday is being marked.