States: Kentucky: Fleming
I went to the Ancestry site and found the information just as you said. Since it is the end of the county, it is possible that the next few pages, after 521, are the mortality schedule for Fleming for 1870. Could she have died about then? Another thing that you could try - go back to the AIS search page. Enter 1870, KY, Fleming. Then in the the page number spot, enter 523. Don't enter anything in the "name" boxes. Run that search and it will give all the names that it has on that page. See if any are familiar to you, people that were neighbors/relatives in 1860 or 1850. If they are not familiar, maybe it is a mortality sch. page. You could also look up a few in 1860 to see if most of them were elderly.