I know that the topic ended a long time ago but I want to comment xD
I always thought that, initially, Celestia saw Twilight more as a weapon ... I mean, the elements of harmony originally had no carrier, now that she has one and this element '' thinks '' politically it is not convenient to have him as an enemy.
So much so that even Celestia, despite having developed an appreciation for Twilight, always resorts to it when a problem occurs.