I am a 15 year old girl and currently dress size 6 how can get to 12 fast?

There is no healthy way to go from a dress size 6 to a size 12 in a short amount of time. Doing so could lead to disordered eating and other health issues. Rapid weight loss can be very dangerous and should only be done under the supervision of a medical professional. If you are concerned about your weight, please talk to your doctor or a registered dietitian. They can help you develop a healthy and sustainable weight loss plan that is right for you.