I once battled with Shauna on a whim on the Maison and she actually did pretty solid (though granted it was just regular and not super)
Her Sylveon withstood a lot of abuse while my Volcarona (my lead poke of that time) was getting downed pretty early in XD --- The Nanoha that you've always admired is an invincible Ace who will not lose to anybody.
Trevor was smart when he was my partner and knew to use Earthquake when my Pokémon was a flying type, rather than stupidly use ineffective moves like the generic partners do. --- Shedinja uses Shadow Ball. Pikachu be dead.
When I was first attempting Maison, I did Multi Battle with Shauna. Most went pretty well but one painful match I watched her uselessly spam Helping Hand after my Pokemon had already fainted. I have no faith in the AI after that. >_<