I like them - I think the proportion of Sweetie Belle to Rarity is off though. She's itty bitty.

This is coming from someone with no art skill whatsoever, so whatever you do is Michelangelo compared to me ooBrony, but maybe take them to an art teacher in your area (at a university or art school), with some examples of the source, and see if they can give you some tips/lessons on how to draw Rarity to your specifications.

Keep up the good work and stay fabulous

I like the drawing where you drew Rarity

But they are pretty good

Keep drawing, and you'll get better at it.  That's it.  My pony drawings now look very different from my pony drawings a year and a half ago.  Drawing something (or somepony) you care about is even better.  Keep drawing what you love.