End it. You don't sound like you want kids at this point and she does. There are plenty of guys who want kids in their late 20's and cope with it but you're not one of them. Why string her along and make life miserable for both of you? She should have known better that she was setting herself up for heartbreak but I guess she was hoping that she could have the whole package before the clock runs out, but that's just fantasy. Great sex does not necessarily mean love or indicates that a mature relationship is forthcoming. End it. Unless you're committed to embarking on this journey which requires 100% maturity and commitment then end it. Believe me, you're not doing her any favours by staying and it's a bit presumptuous on your part to think that you are.