According to Brianne Drouhard at her Potato Farm Girl Blog the mystery girl on the flying unicorn is in fact Amethyst of Gemworld which will be getting her own short as part of DC Nation separate from the girls of Super Best Friends Forever.
Brianne was even kind enough to share some footage of Amethyst in flight. Yipee. This looks really cute, my little 6 year old princess will love it. I am still not sure how long these shorts will be, but I think DC Nation is shaping up to be quite promising. As much as I live Batman, there is a certain joy I get every time I see a new hero or heroine animated for the first time.