Sarah, please copy me

Sarah loves to follow her sister Sharon, follow what she is doing, speaking, and singing... Some times, Sharon got annoyed, and didn't like sarah copy her. So, here is a story. One day, Mommy drove them to some place. Of course, Sharon was singing some songs in the car, and of course, Sarah copied her. It was Ok at the beginning. But after a few minutes, Sharon told her sister: don't copy me! Normally, Sarah wouldn't listen to it, and continue to copy Sharon. That day, quite strange, Sarah agreed, and didn't say a word, and was very quiet afterwards. You may guess what happened next. After a while, Sharon was boring, and asked Sarah: Please copy me!!