Princessa appears 65 times at rank 1600 on female pets — a double-S variant of Princesa, which itself is the Spanish form of Princess. The additional S in the spelling likely reflects phonetic transcription by someone writing the name as it sounded to them, making this partly a registry artifact of orthographic uncertainty around a spoken nickname.
The Spelling Artifact
Spanish speakers saying "Princesa" with emphasis may produce a sound that English-hearing registrars or owners transcribe as Princessa — the double S appearing as a phonetic accommodation. This puts Princessa in a similar category to other variant-spelling names where the sound was clear but the orthography was improvised. It effectively merges with Princesa as a registry variant rather than a distinct name choice.
The Royal Register
Despite the spelling uncertainty, Princessa functions in the same owner-type space as Princess and Reina — a small, female dog whose owner has decided she rules the household. Chihuahuas, Shih Tzus, and toy breeds are the primary recipients. The double-S spelling gives the name a slightly more ornate visual quality that suits the aesthetic.
The Counter-Reading
Princessa's main liability is the spelling — no two vets will write it the same way. But owners who use it are not primarily concerned with orthographic consistency; they're concerned with how much they love their dog. That's a perfectly sufficient basis for a name.