Little is known about Kissy Missy, but through gathered information, it is learnt that she was made in 1985, a year after Huggy Wuggy was created. It is speculated that Playtime Co. made her due to the fact that Huggy rose in popularity, and so seized the opportunity to create a feminime counterpart to further boost the popularity.
This was and still is a common trope in almost every industry to date. Should there be a boy/girl version, it is expected that an opposing gendered-variant based of the original is created to accommodate the original. Whether this is simply to cater to multiple demographics or enforce heteronormativity, (or both,) it usually depends on the context. Recently, it has been confirmed that Kissy Missy is Huggy's love interest.
Chapter 2: Fly in the Web
Kissy Missy makes a minor appearance in Chapter 2, in the Cart Corridors.
She is first seen walking towards the Player, in a fashion similar to how Huggy Wuggy walks when triggering the Vent Chase. Kissy then reveals herself, with the loud siren noises now shifted into a calming melody. She looks at the Player for a short moment, then notices the lever nearby. She proceeds to pull it, albeit unsuccessfully on her first try, but manages to get it on her second try, and opens the gate. As the gate slowly rises up, she looks at the Player once more, and walks away.