Well, many negative reviews about the game but Primula's character is still great though, probably due to her writing already well-established in the past.
Primula is so smart and mischievous right now who loves keeping secrets, and she is likely the most powerful individual in the story politically, and surely the strongest magic-user since forever. I just hope she will get her own route in a DLC or something. She's the only reason I play Shuffle after all lol.
and yes Primula is an immortaloli according to Aoi Nishimata, I added some of the major plots of hers in https://shuffle.fandom.com/wiki/Primula (skyliet's editing), please let me know if there are some mistakes, my Japanese is not the best ^^".