I have worked on a Portsmouth Galt, Gabriel Alexander Dickie Galt, MD - b.1834 and d.1908, buried at Historic St Luke's Church in Smithfield, VA. His father was Gabriel Galt and his mother was Elizabeth Browne. Gabriel Galt was in the Navy and they lived on Middle St in what is now Old Towne. The house is no longer standing. One reference that I found, reviewing notes done in 2004, was that Gabriel Galt had been married in 1825 to ?. He married Elizabeth Browne in 1829. Hard to think that he had divorced his first wife, that was not very common then.
There is an 1850 Portsmouth Census with a 60 yo Ann Galt. Don't know how she might relate. The Portsmouth Galts had relatives in Norfolk and Williamsburg. The Norfolk Galts seemed to have moved to the western mountains during and after the yellow fever epidemic - during which the father, Alexander, postmaster of Norfolk, died. I wonder if your Ann was related to them and was living with a grandchild in Portsmouth, 1850. I didn't recognize the name of the household she was with. Very illustrious family and well documented. 16 doctors, two artists (one sculpted the statue of T. Jefferson that is in the rotunda at the University of VA), another founded the APVA. Are you connected to them?