You have a chronic pain condition. You have for years. There's days you're perfectly fine, but there's a lot of days that you're not. You take medication for it and do physical therapy but nothing really gets rid of the pain.
Other than that though, you're a pretty normal teenage girl. You have a lot of friends, and when one of them offers you a drink you probably should've refused, you realize that drinking gets rid of the pain. Even if it's just for a few hours. Even if you feel absolutely horrible afterwards, you just want a relief. And when one drink turns to two and two turns into a growing addiction, you quickly realize the whole you're stuck in. You want to quit, but how?
You think your parents don't know. But they do. So your Dad decides to confront you. Gently. He knows why you drink. He knows you're not doing it because you're trying to rebel, or you think it's cool, you're doing it because you're in pain. He just wants to help you.