Female Pig

There are two known instances of Female Pigs, both appearing in the Angry Birds Seasons episode Hogs and Kisses. 

Female Pig (Credits)
This Female Pig is the size of a large pig and wears a pink bow and eye make-up. This pig is seen in the credits of the game and in promotional images, as well as appearing in the game. A plush toy was made of this Female Pig.

Female Pig (In-Game)
The second is the size of a small pig and has a big red bow. It first appears in level 1-1 of Hogs and Kisses.

Cardboard Cutout
A cardboard cutout Female Pig wearing a blonde wig is seen in the Angry Birds Bing Videos. This cutout was used by the Birds to get back at the pigs for stealing eggs.