My daughter is having foul smell from th mucus and in her mouth and she is on keflex antibiotics she will be ok yeah and she losing weight also?

Needs dental checkup: There are many causes of halitosis (bad breath). Bacteria grow in the mouth constantly, and thus even in a normal person, if you do not brush your teeth daily, your breath may smell bad. Your daughter is taking Keflex for what reason? She may have gingivitis, dental abscess, sinusitits, or pharyngitis (infection of the throat), all of these may call bad breath. She should see a dentist first.

Nose?: If the child is on antibiotics for sinus issues (can't tell from your question) and there is a foul smell, be sure your doctor checks for a foreign body she could have shoved up her nose that is causing the odor. If she is losing weight, she may need other workup to be sure there isn't another problem going on. It could be teeth, tonsils, adenoids or something else too.