LET ME TELL YOU SOMETHING ABOUT RARITY. 
Rarity has got to be one of the first “beautiful” character (meaning she wears makeup, spends time on her hair, admires fashion, ect) that isn’t used as the villain or stupid girl who is just there to look good and be adored by men.
She shows girls that it’s fucking OKAY to be glamorous and spend time thinking about how you look. Girls are often called sluts due to their appearance. Dark eyeshadow is something a “whore” wears. Fake eyelashes make you look like a “prostitute”. Yet at the same time they are SUPPOSED to put on makeup for boys. Who wins? Men anyway.
     Yes, Rarity is interested in boys, but she called Prince Blueblood out on his bullshit and stood up for herself. What does this say? Ladies, and most importantly, gentlemen: she looks good for HERSELF. Not for you. For her.
      Going back to the “girls who are beautiful are villains and/or stupid” argument. Think of a Disney princess who knows she is beautiful. Who do you think of? I think of the evil stepsisters, Rapunzel’s mother, Charlotte La Bouff from the Princess and the Frog, The Evil Queen in Snow white….  They are all well developed characters. But what do they have in common? Vanity! They all think of themselves as beautiful! And this trait is used as negative, self absorbed, or in Charlotte’s case, ends up she’s the dimwitted girl.
What do the princesses have in common? None of them call themselves beautiful. All of the princesses need to be told they are beautiful BY MEN. If they aren’t, then they are self absorbed. They need to be TOLD they are beautiful.
Rarity doesn’t stand for that.
Rarity is fully aware of her looks and taste in fashion. Yet this lovable lady stands up for her friends and is aware of their individual beauty as well.

In the end, yes, she is dramatic. yes, she is beautiful. yes, she wears makeup and gets her hair fucking permed and gets her hooves done at the spa. But guess what? She’s an amazing, smart, generous, caring, encouraging, supportive character who will stomp all over you and flip her hair while doing it.