The Winchester's 'Cousin'

We all know about our very own and beloved Winchester boys. They travel all over the country to fight of demons and evil spirits. One day Sam has a vision. Not just any other vision either. He sees a girl and he his determined to find her and assumes she is another family member involved within the hunting business. Once they find her, they realize she isn't a Winchester or even a hunter. Have they taken the wrong person? An innocent girl? Or was she just what they needed? Will she help fill the hole John's death left?