Well yeah rays develop their pattern over time. If you take a look one the pic i uploaded on my pearl male you see an p14 looks when mature. The black large ray with many small spots is an galaxy or p14 as they are known as. I did say she might have some pearl in her not that it was an pearl.
What did you buy her as? Is she wc or is she bred in captivity? If wild what locality is she from?