So because Twilight missed the Wishing Star the first time, she used magic to make it come every year.
No… The Wishing Star is Twilight Sparkle. The ponies of the first generation after Equestria’s collapse had chosen to make the time when the shooting star stopped once a year an important reminder day to wish her back. It coincides with the beginning of winter, which is why C3 is released at the end of November rather than at Christmas time.
All the signs are there. Twilight Sparkle is so central to the Wishday - and the very shape of the star based on her cutie mark - and her magical symbol, an eight-pointed star, can be seen on the star. Additionally, it emitted a certain color recognized from Twilight Sparkle. That’s why no trailer shows the Wishing Star. This is the big surprise. And perhaps the biggest shock since the revelation of the Harmony Tree after the G5 movie.
At least we know that Twilight is alive, and that she is in the G5. But she will never return, because Sunny wants to find her - and set her free. And it is possible that the intelligence in the Unity Crystals that “greeted” the Wishing Star wanted her. The only one who can now set her free is the one destined to succeed her - Sunny Starscout.