Your obscure background filly has arrived, Cheeryfriend!
Fun fact: Instead of Cutie Mark Chronicles (in which this filly appears following Dash’s Rainboom), I used Cutie Re-Mark for much of the background. After all, it’s exactly the same shots from the original... or so I thought! The Season 5 shots were remade to not only change rendering, but the animators took the opportunity to subtly correct their early season errors of unicorns & earth ponies standing among the Cloudsdale crowds. It’s the same pony palettes too (Twinkleshine, Sea Swirl, Ruby Pinch, etc), except as pegasi.