What can a 19-year-old do about these lines and shadows around her mouth? (Photo)

Fulness of the lower anterior cheek (area next to the corners of the mouth) is usually caused by fullness of the buccal fat pad. This is very common in patient with asian background. Additionally, if the patients have not adequate lateral cheek fullness the lower  face may sag causing "virtual excess of skin" near the mouth that could be confused with jowls and mouth shadows.Buccal fat removal is the plastic surgery procedure that helps to achieve a think face, specially in patients with asian features. If the patient has mild lower face skin sagginess, it is important also to undergo lateral cheek enhancement with soft tissue fillers like voluma at the time of the buccal fat removal to achieve a more chiseled face. 

After reviewing your photos, it is apparent your mid face is very full. This is hereditary and weight loss will not help. You may benefit form a Chin Implant as well (a side photo would be helpful). The small pre-jowl (cheek shadow) is a result of the heavy mid face pushing the cheek mass forward. Buccal fat removal would help this quite a bit. Find a surgeon with expertise in this procedure for best results. Fillers are to be avoided with your anatomy as they often worsen the problem. Best,