Are you absolutely sure this is an infection? How long has it been like that? Did the child have a spot there since birth, and it has recently turned bright red and swollen? If it is red, warm or hot to the touch, and painful, it is likely an infection. If she was born with any sort of birthmark there, that is recently turning bright red, bleeding, or swelling, it could be a hemangioma that is growing.
Regardless, if parts of her tongue is falling off, this is undoubtably very serious. I know there are parts of the Middle East with very good health care. It depends where you are. The larger cities have the better facilities.
I wish I could give you ideas about what to do, but without knowing what is wrong, there is no way to give you any treatment ideas.
It sounds horrible for you. Is there no way to get her on a course of antibiotics? If you are totally away from health care, you can try rinsing the area several times a day with vinegar. However, there is nothing better than taking her to a doctor. Can the doctor who "can't find the problem" refer you to another doctor?