Quinceañera is the Spanish term that can refer to the young woman celebrating her fifteenth birthday.
The word is also commonly used for the celebration itself, so context determines whether it means the celebrant or the event. Its connection to quince años identifies the central milestone: fifteen years of age.
Other Spanish terms appear in the ceremony but have different meanings. A madrina is a female sponsor or godmother-like supporter, a dama is traditionally a female attendant, and a chambelán may be a male attendant or escort. None of those words names the birthday celebrant.
English-language usage often keeps quinceañera as a cultural loanword. Spelling the ñ correctly matters because it is a distinct Spanish letter and part of the standard form. The masculine counterpart, quinceañero, may describe a boy celebrating a similar milestone.