I have the hypothesis that Spitfire only had to learn the lesson of Loyalty once. I'm pretty sure that when she was smacked by Rarity in Sonic Rainboom might have messed up her memory. Evidence? In The Best Night Ever she asked RD to hang out with her, but she seemingly forgot. In Wonderbolts Academy,she forgets how great RD is. BTW,if she hadn't betrayed Soarin, Tirek would have won. Read Friends Forever issue Eleven. The kids are more of jerks than her. They could see she was nervous but they just kept bugging her even more.