The AST/ALT pattern is already showing signs of alcohol use. There is no "safe" recommendation for drinking (although at age 19, note that she is underage in the United States). The length of time it takes before more permanent damage varies from person to person, but she is already doing damage with the elevated AST/ALT.
Other possible symptoms would include right upper quadrant pain, fever, jaundice or anorexia.
I would encourage that she obtain counselling on alcohol as well as a discussion of the effects of alcohol with her personal physician.
Followup with your personal physician is essential.
This answer is not intended as and does not substitute for medical advice - the information presented is for patient education only. Please see your personal physician for further evaluation of your individual case.
Kevin, M.D.
Medical Weblog:
kevinmd_b