I read somewhere that Spike was written to fall in love with Rarity at first sight to show to the audience that she was just
that gorgeous. Something like Lauren Faust believing people wouldn’t realize she’s supposed to be beautiful because they’re ponies, or more beautiful than the others because they all share the same body type and art style.
Equestria Girls didn’t have this ‘oh, you sweet summer child’ issue of people possibly not realizing how attractive Rarity was supposed to be, of course. So,
how did they show said attractiveness?
By giving her some
killer hips. The widest in the entire spinoff, if I’m not mistaken; not even Adagio Dazzle or Principal Celestia can compete.
It never ceases to amuse me.