Tayla Parx has come a long way since she played Little Inez in 2007’s Hairspray at 12 years old. She transitioned from acting to songwriting when she was 19—and now, at age 25, she already has credits for powerhouses like Jennifer Lopez, Fifth Harmony, Janelle Monáe, and Christina Aguilera on her well-stocked résumé. But 2018…