We had similar issues with my step daughter, she wanted to take alcohol just because "everyone else was".
Peer pressure is a terrible thing at that age.
We knew she would probably drink if her friends brought some along but we stuck to our guns and she went off with no alcohol Kopparberg type cider. The cans are identical to the full fat version.
We also warned her about the dangers of drinking something someone else has given you, alcoholic or not, even if you think it's fine cos you know them. Teenage boys in particular can do dozy things 'just for a laugh', she took that message really well and said she think she might have had a drink spiked at a previous party because she wasn't drinking and had felt really odd.
Turned 16, she takes some alcohol, some non alcohol. Does depend on the party, who's going and what she's doing the next morning. Never is it a bottle of vodka or bacardi!
We did let her and a friend take some strong cider out of the fridge once, it was too much for her and she threw up and has checked the alcohol content of anything and everything since then!
We're lucky, she finds drunk people really annoying and isn't interested in becoming one of them.