Sea Swirl, behind Pinkie Pie.
At Twilight's welcome party.
She is barely visible in the bottom left part of the image.
Ponies are partying at the library.
Chatting with Sassaflash.
In the middle reaching up.
Near the top of the pony pile, above Scootaloo.
In the bottom right corner.
Sea Swirl seen on the right.
If you look closely, you see lots of hat-wearing Sea Swirls in the crowd.
At the same time, she's with Canterlot
's elite, dressed up to the nines.
Still all over the crowd.
There she is, right of Rarity
Rudely cut off, we can't see her reaction upon the sudden party.
Something wrong with your drink?
And how did you manage to hide your horn?