Susanna does not seem, at present, to be a member of any of the Smith families living in the village - not that there were many - in fact in the years from 1588 until 1771 they numbered less than fifteen. Five of those can be found in the late 16th to early 17th centuries listed under the spelling of Smyth, the rest are listed under the modern spelling and lived in Barkby between 1710 and 1771. Of the later Smiths there are just two families - one headed by John Smith whose wife was Elizabeth Plant and a John Smith whose wife was Mary and as just mentioned Susanna cannot be linked to either of them.
So who was Susanna? Why was she alone in the village and why was she there? I think that the answer to these questions lie in domestic service.
I haven't proved that Susanna was employed here and when researching your family history you must never jump to conclusions, however Susanna is typical of the female 18th century domestic servant - young and unmarried. Maybe the next clue to Susanna's ancestry is that she was not a hired stranger, but was distantly related to someone who already worked at the house or new of a position there.