No, you're just looking at it wrong. Yes, she gave the smallest diamond to spike, but what if she just didn't want to be bothered with Spike taking care of her cat? It may be a matter of "you're going to get in trouble with this, but if you want to, fine.". Also, she didn't MAKE Spike give it up, she just admired the shape of the ruby, and she might of not ever had one like that. Who knows? She was into being more popular because of the wings that she admired very much, but noticed the lesson at the end of the episode. Also, being a Canterlot pony was one of her dreams, so meeting Fancypants was like a dream-come-true for her, and she actually got invited to that Garden party, which was also another dream. Don't forget that she was working on a new line of clothes, and Sweetie Belle made her lose track, and Rarity shouldn't be forced to get dirty if she just plain out doesn't like it. You forget the other part of the episodes, where she sides with her friends, goes to the sisterhooves social with Sweetie Belle, and where RD performed the Sonic Rainboom anyways. Rarity is actually generous if you actually take a moment to look at the other parts of the episodes. Also, in Wonderbolt Academy, she also saved the other ponies too, so don't take that as a "rarity onlee" thing, because it wasn't. Twilight, and the rest of the gang got saved too.

