>>42559770
Rarity is the most complex of the mane 6. When you're young or autistic, you see the surface that's vain full of vices like making others do the hard stuff so she has an easier time herself or just getting too excited about hitting it big in the jet set to realize what she's doing to others.

Growing older is realizing that's just a thin layer on top of her heart of gold. She cares for her friends and isn't selfish in the slightest and is ready to abandon her dreams for her friends if need be. I think she's the only character we see do that exact thing, toss away her dream of being a part of the upper class for her friends. She's headstrong, intelligent (in a different way than Twilight), hardworking, and, yes, vain.
In other words, she's complex.