I think that your instincts are right — you should cut it off completely, unless or until she is really for a commitment. Otherwise, she’s going to be using you until someone better comes along, simply so she doesn’t have to be alone or be without sex. Lots of people have ex sex because it’s familiar, safe, and convenient. But that creates a relationship and since she’s not giving you the commitment you want, I don’t think it’s a good idea for you. It’s going to be painful to break up again — because it really is a second type of break up — but sometimes that’s what it takes to really move on. So either don’t go to your Washington DC weekend — or do go as the last blast before the break up — and then move on. If she tries to contact you, explain that you’re not interested in an interim situation. You want all or nothing and you’re not willing to do anything in between any more.