There's no sense in taking a break. There are no 'breaks', 'recess', 'vacation', or 'holidays' in any relationship. It is ongoing. Yes, you will experience problems and disagreements, but if you can't learn to communicate and be honest, t hen you may as well break up. And even if you did resume things with her once she's 18, the problems you both avoided will STILL be there that you have to acknowledge and discuss together. So, why not now instead of a year later?
Yes, you both are on different life experiences. You have an idea of what adulthood is and what comes with it. She doesn't. She still has slightly the mind of a child near the end of her teenage years, and usually for teen girls, they really do distort the idea of love to where to makes them not think straight. Bringing up marriage only after 4 months of dating is hideously insane, because there's so much more you both have to discover about each other before that happens.
So, honestly, sit her down and be honest with her.