The farm girl is encoutered at the Farm. When encoutered she will say "Hello there little fellah! Boy, am i gonna have some fun with you!" She is a big, tanned, buxom, broad shouldered girl, with long blonde hair.
She is only encoutered at the Farm.
The only mutations to happen to the Farm Girl are an increase in size. Starting at 6 feet. If she is 8 feet and you are exploring the farm she can capture you and take you to be Branded.