My friend overdosed she threw up and drank water...

Is throwing up enough in this case ?
although we are not fully aware of the drug that the patient overdosed with , but throwing up isnt enough , in this case , visiting ER is a must to make sure of patient health , and the following should be done :
1. Know the medicine and the quantity intake 
2. Inform the doctor about the medicine taken and the expected dose
3. general examinations are performed for the patient including vitals tests , blood tests including : CBC / KFT / LFT 
4. The condition is monitored for 6-24 hours
Possible side effects of overdose :
Of course, and regardless of medications side effects , taking medications in overdoses is always harmful to the human body, which may lead to health risks such as:
1. Acute side effects
2. Gastrointestinal infections
3. Liver poisoning
4. Kidney failure
5. Failure of bowel movement
6. Loss of consciousness
7. Shortness of breath
8. Blood clots
9. Death
General advice:
1. Keep the medicine out of the reach of children or people who have previously taken medicines without medical necessity or in large quantities
2. Know more information about the medications at home, its risks and side effects