what do I do if I find that my sister is on drugs?!
Angry outbursts, mood swings, irritability, manic behavior, or overall attitude change Talking incoherently or making inappropriate remarks Risky behavior, such as driving under the influence of drugs, starting a fight, or engaging in unprotected sex Secretive or suspicious behavior: frequent trips to the restroom, basement, or other isolated areas for privacy while using drugs Deterioration of physical appearance and grooming Wearing sunglasses and/or long-sleeved shirts frequently or at inappropriate times Frequent absences from work or school; drop-off in quality of work or grades Neglect of family responsibilities Evidence of money problems: frequent borrowing, selling possessions, or stealing items from employer, home, or school Legal problems rooted in drug use: arrest for driving under the influence, possession of a controlled substance, disorderly conduct, or stealing
if any two of these are there,u can suspect a drug abuse...
Talk to your parents about it. You're not her parent, and your parents will be able to discuss it with her in a rational, mature fashion.