Apologies everyone I am still mid update on the Arena list. She is in 2 waves...so its like this...
Wave 20 - this is the last playful wave from Cutie Mark Magic - ribbon in hair - Fluttershy, Nurse Redheart, Princess Twilight and Starlight Glimmer
Wave 21 - first wave of playful from Explore Equestria - with alice band - Applejack, Fluttershy, Rainbow Dash and Starlight Glimmer
Wave 22 - second wave of playful from Explore Equestria - with alice band - Pinkie, Pursey Pink, Princess Twilight and Rarity
If you have not seen wave 20 by now on shelves you may very well not see it at all. But you should therefore go straight into wave 21. So if you miss her with the ribbon, you should get her version with the hair bow.