The name quinceañera is Spanish, and its spelling includes the distinctive letter ñ.
Quinceañera is formed from quince, meaning fifteen, with a feminine ending. The word identifies both the young woman and, by extension, the celebration associated with her fifteenth birthday. The masculine counterpart is quinceañero.
The ñ is a separate letter in Spanish, not merely an accented n. Its pronunciation changes the sound of the word, so quinceañera is not accurately written as quinceanera in careful Spanish orthography, although the unaccented spelling appears in some English-language contexts.
Portuguese is the language associated with Brazil, where comparable events are often described with terms such as festa de debutantes. That linguistic difference helps explain why related celebrations have different names across the region.