Inscription on the back: "aunt Phoebe Shearer Spinster sister of Grandma (Mary Ann) Smith"
Phoebe Shearer was born in Pennsylvania in 1827. She had many siblings, including her sister Mary Ann Shearer who later married John Keysar Smith. I can't find much else on Phoebe, though the inscription on the back of the photo indicates she never married.
If you know who this woman may be, let us know in the comments!