Just a note: I know for sure that Superman the Gastly is going to evolve during training. However, Larvesta may as well. It's a small possibility, as she's definitely going to get worked the hardest, simply to keep ahead of the rest of the group.
Even though she's timid, she knows she's fairly strong, and wants to remain that way out of fear of what might happen if Frostbite and Superman are able to get the jump on her.