I thought about Trixie, and while I realize my idea has it's flaws I still thought it would be fun to share.
The idea is about Trixie. Why DOES she hate Twilight so much. No clear explanation past the obvious but petty reason. I had the thought, what if at a young age Trixie did seek out to be the center of attention. She worked hard, to perfect her magic early on, even if she might use her magic to make fun of others to show how great she was.
Her parents decided to contact the Canterlot school to see if Trixie could get in, even Celestia was amazed with her magical talent. Unfortunately for her Celestia also had her eyes on Twilight in the other room taking her test. And just before Trixie successfully hatches the dragon, a magical surge happens and Twilights spell mishap distracts everyone including Celestia so Trixie ends up getting ignored, failing her test and dropping out.
Even with the promise that she could come back and try again next year, she has always felt a sort of hatred towards Twilight. She worked hard to get her powers, and surpass every other pony, and no matter what happens Twilight seems to be just handed her victories. In her second battle against Twilight she learned that Twilight is more powerful than just her magic and it humbles her a bit. But I thought of a great way to have a 3rd encounter.
What if season 5's villain has a way of disheartening all the ponies, each one needing to find their own inspiration to keep fighting this opponent. Such as a political campaign where the villain is tricking all the ponies into hating twilight somehow. (could have magic involved)
So Twilight becomes down and out ready to give up. But as she's drinking a shake a familiar blue pony comes up, and tells Twilight she's an idiot for wanting to give up. She explains to Twilight why she always hated her. And that while she still does she's learning to cope with the fact that Twilight will always be the special pony in everyone's eye, and that she was destined for other things.
She tells Twilight that in their second battle with the Alicorn amulet, she realized just what made Twilight so special, and it wasn't her raw magical talent, but her ability to make friends and become stronger through the bond that they had. Then before Twilight can talk, another pony (a friend of Trixie's) comes up and they leave together, making Twilight realize the true strength they have and uses the ideals of friendship to win the campaign/fight/whatever.
idk, it's a vague idea but I thought I should share it.