The character Selya is from Balagtas' epic poem "Florante at Laura," and she is a fictional character, not a real person.
Selya represents a kind and virtuous woman who is in love with Aladin, a character in the poem. Her name is likely inspired by the Spanish word "Selva," meaning "forest" or "jungle," which reflects the exotic and romantic setting of the poem.
While Balagtas based many characters in his work on real people, Selya is purely a product of his imagination, created to enhance the story and illustrate certain themes.
Therefore, it's inaccurate to say that Balagtas named Maria Asuncion Rivera as Selya.