This is a difficult problem. It is possible to take Accutane a third time, but as you realize, the chances are that any remission will be short, and since your daughter is only 18, she can't very well keep taking Accutane over and over. Lasers may be worth a try--they're safe, but results are often partial and brief. Oral and topical antibiotics are probably worth at least a try. Even though they didn't work before, they may be more helpful now that Accutane has modified the oil glands, at least partly. Other possible therapies are oral contraceptives and the drug spironolactone. Your daughter should take up these and perhaps other therapeutic possibilities with her dermatologist.
Best.
Dr. Rockoff