Headcanon: After the poor treatment the Wonderbolts, Rainbow throws in the towel and quits....this time for real. Despite her friends trying to conceive her to give them another chance, Rainbow's decision is final. However, when she does join a group, but not the Wonderbolts, the Shadowbolts! Her friends, her parents (Bow Hothoof and Windy Whistles) and her adopted little sister (Scootaloo) are in shock at first, however when they see how much the Shadowbolts treat her better and how happy Rainbow, they support her, despite the rest of the Mane Six feeling sad that their friend wants nothing to with the Wonderbolts anymore. Rainbow is now as happy as can be now that she's part of a group that doesn't treat her like a punching bag, in spite becoming rivals with The Wonderbolts...

Note: Don't worry, Rainbow doesn't become a villian.

Note 2: For my headcanon, the Shadowbolts are real and instead of being performers or soldiers like the Wonderbolts, they are vigilante superheroes. This was based on an idea by King Grover: https://youtu.be/u003OBHXl7A?si=Jmyf1z-4osRoBoXs