Author of FFVII: Lifestream & FFVII: Reflections
I get it every time, but she's typically the only one with a level 4 limit by that point. She never leaves my side as long as she's alive, and it doesn't take quite as much grinding as you think if you keep her in Fury status and let her do most of the killing (a magic materia with All or the Matra Magic enemy skill does that nicely). Makes the Temple bosses easier and also lets you get some use out of one of the best limits in the game. Have Aerith whip out Great Gospel and then laugh at Demon's Gate as you take him down.