what does "thats what she said" mean?
Generally it's a bit offensive expression, which is aimed at changing a meaning of what someone said in favor of the one who says it. Example: "- I like it. - That's what she said" BTW In which language class did you get taht question? hahahaha hilarious :P Are you from a US school? :P
It's used to quoting someone's utterance, for example: - "He's very friendly." - That's what she said. I hope you'll understand my answer :D