Because the count was annoyed but didn't want to just let her go, he brought her to their house in the dark forest where they held the children they kidnapped. The room in the back of the house soon became hers from then on.
They had only given her just the necessities like water and food. She was always kept in the dark since the count realised it seemed to have made her silent and more calm. Because, when in the dark, no one would even know someone was there. However, if the light fell on her room and she saw something, she would scream and just attack anything.
Basically, like a thoughtless puppet, her life still hanged despite losing all the hope for a normal life from then on.
However, the counts used her as a way to scare off the disobedient children they brought there.