I am writing this against my husbands advice,<snip>
I am sorry about your young friend. That was a very unfortunate diag. and for them to have made such an error is really very bad medicine. I have been involved in an HIV/AIDS Organization for about 10 years and many of our clients have been involved in risky behavior which may or may not involve drugs and alcohol. Many turn to the behavior that got them to this point in their life. They are all wonderful people but they make some choices that continue to hurt them. I am sorry your friend was pushed to mix drugs and alcohol, that is always a bad combination. But, you must not blame yourself. You did nothing wrong. She took your pills and then drank, you had no part in that. I hope you can focus on the good that your brought into that young girls life because that is what you really gave her. It is so easy for all of use to blame ourselves when something goes wrong. You sound like a kind caring person and I am sure that is what was important to her. The rest was up to her.
Please be gentle on yourself.