Namechagaiiin, I had to laugh at you and friends sitting in the cemetery getting drunk. My son and his friends used to sit behind the church on Blackheath doing the same.
Mine had a fifteenth birthday party, we were here. Loads of people came including some 14 year old girls who went to a nearby girls' school. They used to go around with them (still good friends donkey's years later). A couple of the girls' dads drove them over, and collected them just after midnight.
We had provided food, soft drinks and some beer, I also made a fairly benign, decorative punch.
The girls brought vodka which they'd nicked from their parents and had hidden in their bags and coats! Vodka went in the punch and down their throats. One of them wandered out into our garden and fell asleep on the ground. I was almost frantic but she got up, said she'd just felt a bit tired, went back into the house and carried on dancing.
Hardly anyone touched the food. The party was noisy and verging on riotous in a good humoured way.
They were always getting drunk, especially the girls.
They are now all respectable forty-somethings, no harm done.
Your girl will be all right, op. You are right not to make a big issue out of what is normal teenage behaviour.