At the cemetery office, I asked about her grave site. They didn't have a Harriet Barkley who died in 1900. They did have a Harriett Barclay who died 16 November 1900. Close enough, I figured (my correspondent warned me about the different spellings). She is buried in Section 1-7, Block 43, Lot 4.
The office gave me a map for the cemetery as shown below, with a "local" map
below. The "local" map has numbers corresponding to the deceased who are buried within a 15 foot radius of the target person, who is marked with a star on the lot map. Information about the target person, and the names of the "neighbors," are also on the page to the right of the cemetery map. The page provided by the cemetery is shown below:
The dashed line to the right of the lot map is the cemetery fence, and the road above the lots is the road heading east to the fence.
Unfortunately, not every grave has a stone - whether above ground or in the ground. I found the stones of #07 John Nicholas, #03 Annie Chambers, and #02 Fred Chaffee. Harriet's grave is about two feet east of Fred Chaffee, in the center of the grassy patch shown below.