@animefan14  
i actually dont read fanfics.  
the side actually goes down past the part of the hip where any type of underwear will be visible so she is wearing them.  
the inspiration for the design came from chinese dresses,i was suppose to draw a back view of this to show that the back of the dress is very loose and goes down to the hip  
google images of backless chinese dresses and you’ll see a resemblance

Did you happen to read the fanfic “A Weekend Maid for Spike” on FIMFiction.net recently or at all?
 
I ask this because this image that you’ve created with Rarity and that dress really seems like that same dress that she wore on her date w/Spike to a fancy exclusive Ponyville restaurant, and one that she couldn’t wear any kind of underwear at all with it. Only thing would be that the color in the story is a royal purple…
 
That’s what I see first. Can’t help it–I really love the design. Sensually and reserved at the same time. Plenty out there with even more to the imagination.