Page 7....who's that????? Oh no
I find it hard to believe that it was one of her classmates. The person looks like an adult.
Except that, for the most part, people who are in their late teens are fully grown and don't look all that different from adults, especially if you can't see their face. This is especially true for girls. They reach their full adult height sooner.
What is really amazing is that her friend was thinking she was kissing a man when the person she was kissing had a very feminine hairstyle. I guess the trenchcoat probably masks her curves and she is quite tall, but still, most guys with long hair don't wear it loose like that.