Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
2. Persa, ae, f., = Πέρση, daughter of Oceanus, mother of Circe, Perses (the father of Hecate), Æetes, and Pasiphăe, by the Sungod, Hyg. Fab. praef. fin.; also called Perseis, Cic. N. D. 3, 19, 48.
Hence,
Persēis, ĭdis, f., v. 2. Persa, B.