Oh, wow... I'm not even sure where to begin. Obviously, that's not something the runner would have actually flown nearly anywhere-- she would have been under the colors of her owners (principally British). Government-owned runners would have had government flags (and also sailed under neutral colors). So this really couldn't have been anything except a "house" or shipping line flag, IMHO.
The piece itself is obviously a modern reproduction. Where did you acquire it?