Remember, take what Jeff says with a grain of salt. Jeff does know details from the game development process, but he likes to play fast and loose when he gives any info about the games. In this update she was never going to win, that doesn't mean that is how the true ending will go. For a game with multiple paths only one path can be considered canon. For example, Sunshine Love is about to show the wedding of Sophia and Xianne from Melody. Now, in Melody, you are free to keep Sophia and Xianne just friends, that just isn't the true outcome for those characters. It also describes Sophia as Melody's former band member. Again, that depends on your choices.Except that we have it on record from Discord that she was never going to win the competition, no matter what you did. They might change that with the December update based on the feedback they've recieved, according to Jeff Steel, but it still might not happen.
The dev team have to choose what they consider the canon ending, and work from there. They probably shouldn't have revealed Kristina in Sunshine Love before the end of DMD Chapter 3. I don't know if I'm allowed to say things from SubscribeStar but Hearsz (The Chief) indicated that the v0.28 ending is not the true ending. The December release will have the true ending. The ending where she fails is considered a valid ending for DMD Chapter 3, but not for the MrDots universe as a whole.