It's been some time since you posted this message, but if you are still monitoring follow ups I am trying to identify Ann Baker Heron (also known as Ann Baker Herring).
She is identified on a slave ownership document as a free woman- a quadroon and the "natural guardian" of Robert, Jane and Ann Bolton Mackie. She also appears as the mother of Jane and Ann Bolton Mackie on their Christening records.
I suspect she is an early Heron family member, born circa 1776. She had two children with James Baker around the late 1790's.