Chances are that what you call "string him along" is her considering you a friend. If someone is nice to you, you might like them as friends but not as romantic partner. So they are nice to you because you are their friend. Women take care of their friends. So what you see as "string along" is a friend caring for another friend. If you can't be a friend with a woman you like is on you to tell her that you don't see her as a friend, you see her as a romantic partner and only as a romantic partner. Sure, that means that the relationship might end right there. But maybe that is what is right if you don't want a friend.

What you dismiss as "friend zone" is a gift, because friends are a gift. And the ones who try to cheer you up when you are down. Hell, they might be the ones to introduce you to a future partner or to take you out for drinks when you have a bad breakup. Or the ones who bring you warm food when you are sick. If you don't value those things, don't deceive her and say it. Say that you only want a girlfriend and that you don't see her as a friend. You would lose her, both would be hurt, but at least no one would be deceiving themselves.