She is arguably the weakest Champion, in a game that gives you many advantages over the CPU. She's also not as involved in the story's conflict as characters like Lance or Cynthia.
Although I actually do like her, in the context of Kalos' culture. If you pay attention to the NPC dialogue in places like the Battle Chateau, the upper class members of Kalos are rotten, wealthy, and unhappy. The game goes a bit deeper into that dirty underbelly during the Looker Bureau chapter. Diantha, beneath all the glamor and fame, is pretty grounded and personable in conversation despite her status. She'll trade Pokemon to you, she hangs out at the Chateau for fun, and talks about developing empathy for her acting career. I think she's kind of cool. But like most of that game, terribly underdeveloped.
