I agree with rejracer. I find that, usually, if I ask myself a question like this, I already know the answer. If you think you should sell it, you probably should.
On the other hand, you aren't going to get the time and money that you put in back. If you don't need the money, or the space, why not hang on to her? I know when I feel discouraged at the lack of progress on a project, be it car or woodworking related, I just make a resolution to do something small every day. Clean an interior part, torque something down, etc. Even 5 or 10 minutes a day can add up to accomplishing something bigger with the car.
A car project is like a shark; if it ain't moving forward, even slowly, its going to die.