Your tongue could not be used without using your lips & mouth. Ji Woo admitted that she's not a singer. As an actress you do what you are told to do. She only did the singing because she was told to by the director. Simon, the website in youtube was just a rehearsal & they were having fun. That's not the final take on that particular part of the drama. Give Ji Woo a break. A bit of kindness goes a long way.