Female Pig

There are two known in game instances of Female Pigs, both appearing in the Angry Birds Seasons episode Hogs and Kisses.  There is also a cardboard female pig.

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. In the scene she appeared in, the Mustache pig fell in love with her.

Female Pig (In-Game)
The second Female Pig is a meduim pig and has a big red bow. It first appears in level 1-1 of Hogs and Kisses, however, it's just a normal pig with a pink bow.

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.