What can be done? 18 year old female with double chin, developing jowls, cleft chin, forehead both too high and too wide (Photo)

You are overly critical about your appearance ( however being a teen, this too is common). You do not have jowling or a double chin.  You do have a mildly retrognathic (receding) chin with prejowl notching. This can be easily corrected with a extended chin augmentation. This will also improve the appearance of the fullness of the submental neck, with out the need for injections. You do have a high forehead hairline but again it is not abnormal. The BEST solution at this time is a creative hair cut and styling. If you are truly interested in pursuing this, please consult with an experienced facial plastic surgeon.

The photographs demonstrate a weak and  recessive chin profile, for which a chin implant can improve. Chin implants are manufactured in a large variety of sizes and shapes which is best determined at the time of the consultation and examination. For many examples and more information, please see link and the video below