you can only work from the known to the unkown, have you found her death/burial/MI? that would give an age at death. Have you the names of her children? their names would help identify possible grandparents, though many amilies did stick to the usual, william ,thomas, john, mary, ann elizabeth etc. however, it can be a help. if you have found more than one candidiate then again, checking naming patterns, deaths etc, will eliminate some. looking at the baptisms of children may also help if you can see the original entries.