Ann Martin Gifford appears to be the daughter of Humphery Gifford and Lucy Martin Ryall. Jane and the other witness Charles Ryall, and also an Ann Martin Ryall, appear to be children of Mesach and Elizabeth Ryall of Maperton. Mesach Ryall of Marston Bigot married an Elizabeth Martin from Horsington in 1806. A Mesach Ryall - presumably the same one - married an Ann Martin in 1797 and had a daughter Louisa in 1799 who is probably the same Lucy Martin Ryall.
I was a bit hasty identifying Louisa with Lucy Martin. It appears they are different people, each was a witness at the other's wedding. Mesach Ryall was also a bondsman for Lucy Martin Ryall's wedding licence. I suspect that Lucy started as Lucy Martin but was adopted in some way by Mesach. Possibly a natural daughter of his first wife Ann, possibly he was the father.
If you're interested in tracing Jane Ryall's family, the Martins look very interesting. The SHC has her grandfather Peter Martin's farm account books, which also contain family information.
https://somerset-cat.swheritage.org.uk/records/A/AOW/78David
