To date the card I went to this site for some tips. The corners of the card are definitely square so that means the card is likely older than the 1870s. There is a border around the photo, one thin line and one thicker one which was common from the years of 1864-69.
I’m running the Twilight Zone tune in my head right now. I took the latest possible date for this card of 1869 and subtracted 12 years to get the possible birth year of Amanda. That is 1857. Then I googled Amanda Kingsley 1857 and got this page. If you scroll down to the first tombstone photo it reads that it is for Lewis Knapp (recall I did not type in the name Knapp) 1838-25. Spouse: Rachel Amanda Kingsley Knapp 1857-1907. I don’t often get such exact information! I could be wrong but I think this is the same person. Then I found this site! If this is her, she has a whole life! I will be contacting this family and asking them if this is her and they want her to come home!