My gut says that is what happened. Her husband died in 1823. His wife died in 1830. Same community.
Also, the grave marker for General Morgan Chrysler has space for two others: his wife and his mother. His mother is not named, but died in 1876. 1870 is the last census with Fannie Groat living with him.
Also, Henry Groat, Fannie's husband, is buried along with their son, John Henry. But Fannie is not buried there.
I'm guessing, but I really think his mother married his father-in-law.