Gretka tells Ciri the story of how she came to be in the forest all alone. Apparently her family was unable to feed her and sent her to 'follow the trail of treats' which would lead her to a well known orphanage in the forest. Gretka got lost chasing a butterfly while following the trail and thus ended up in the predicament Ciri found her in.
Ciri watches over the girl until after meeting with Baron Philip Strenger where she requests that the baron keep her as a cooking wench in his castle. Gretka can be found inside the kitchen of the Baron's castle in Crow's Perch after completing the King of the Wolves quest.