We rarely ever see ponies cross their hind legs…
 
It’s not really in character for Twi, and it’s not exactly a shy expression [uploading title was “Shylight Sparkle”], but I was making a vector to try picturing a character, and I used Twi for a base, and I figured, “If I’m making the vector, might as well finish the base before I start playing with it so I’ll have an extra Twi vector to mess around with.”
 
I was gonna upload the version without her hindlegs crossed, but I’m sure if you wanted one of those you could find one pretty easily on mlp-vectorclub or something.
 
Made a lot of tweaks to the legs, but it’s basically from here. http://mlp.wikia.com/wiki/File:Pinkie_Pie_offers_Twilight_a_cupcake_S01E12.png