> Also, why would she even have Groudon to begin with?

If a 10 year old brat from a tiny town can have it, why not her? 

Because in Omega Ruby she kind of takes command (albeit badly) of Team Magma as Maxie kind of gave up for some reason. I'm basing this off the Delta Episode. So Team Magma gets Groudon back because stupid reasons and the Orb was never hard to get from the beginning, that and I just like that Pokemon.

Edit: My apologies, I tried to justify a little too much something from POKEMON. 

Real answer: Because Gameshark.