Instead of calling it time-out, how about calling time-away...? That means that they don't just sit there cuz they were bad, but they sit there quietly and think about why they are there. Instead of time-outs being a negative thing, u can turn it into a positive by making them know that they behavior was not acceptable and now, they have to sit in time-away and think about their actions. And remember, one minute of time-away for each year. So, never give five minutes to a child who is only two years old. A one and a half year old child sits has to go for a minute and a half.....get it?
Next, try and not use negative language. And never use good gir or bad girl. When u say bad girl, ur are basically labelling them. And when u call them a good girl, so does that mean that they are bad all the rest of the time? Use encouraging terms and words, but try and stay away from " good " and "bad". Instead of telling her what not to do, tell her what to do, and what is postiive behavior and what is acceptable.
One last thing, are u sonsisten with ur time-outs? If she walks away from it, do u place her there again? And, what other measue do you take to discipline her? Next time, take away a toy that is very dear to her. Do it the second she hits u. And make sure that u explain why ur taking it away. If you keep consisten and give consequences for her actions, she will get it in the end! Good luck!