Sooo, yeah. For all intents and purposes, Groudon and Rebeca are two sides of the same person. For the most part, she will stay as "Human Rebeca". "Groudon Rebeca" will only show up if/when she goes Primal. She can only go Primal if she gets her hand on the Red Orb, and if she gets worn down enough she will revert back to her base level or die from placing too much stress on her body.