meaning of 'talk in'
I need to understand the meaning of the first sentence of the text below:
'Sarah only talked in stories. If you asked her how she was, or what she did at school, she just looked at you like you were the most boring person in the world. What she wanted to talk about was her favorite TV shows and books, usually all mixed together, over and over again. Tonight, there was a new character at least: Lucy the puppy. Lucy was chased by mean dogs; Lucy got thorns in her paws; Lucy was lost and scared and needed rescuing.'