Your question does not describe how you own the property 6.2 acres of land. For instance, is the property owned as a joint tenancy? Check to see what it says about your ownership in the title documents for the property. Your right to act depends on the type of ownership you have. For instance, if you do own the property as a joint tenancy, then you may not have the right to remove property of someone who was invited to the property by your girlfriend. If you consult with a local attorney they can tell you what your rights are for the property if you bring your title documents to that attorney for review.