You can survive without her and you will, even if it feels like you’re drowning without her. It’s not true, you’re not actually drowning, it only feels that way. And it won’t feel like that forever.
Time helps. You need time. You’ll start to breathe normally again and you’ll live your life and spend time with your family and your friends and someday you’ll realize you moved on. You’ll realize that it doesn’t hurt as much anymore. You’ll find someone else, something that I know seems like it’s impossible and something that you don’t even want in the least, but the point is that there is a future for you without her. You’re so young. I promise you, it hurts for a while, but it gets better.
Don’t try to get her back. Why do you want someone back who says they don’t even feel as strongly about you as they used to? You have to know when to let go, when to recognize that a relationship is ending and should end. Accept it, grieve for it, and then move on.
You are strong enough to get through this. Heartbreak helps you understand and appreciate love far more than those who have never had their hearts broken. It’s a way of life and it’s getting you one step closer to finding the person you ARE meant to be with.