I was planing on doing a comic about Luna’s defeat (this is only 1 scene), but I have a heavy schedule this year (maybe someday).
In this scene both (Luna & Celestia) are falling unconscious from the sky, Celestia wakes up first and has to make a quick decision.
Banish Luna to the moon before she wakes up or try reasoning with her with the risk of battling again.
So giving one last look to her sister, Celestia opens a portal beneath her and Luna falls softly and unconscious into it.
MLP FIM Hasbro