The source I have for her marriages is this;
The Decendants of Hugh Brent, immigrant to the Isle of Wight County, Virginia 1642 and some allied families, page 234.
Henry Lawson...He married by 1709, Mary Kelly the relic of John Kelly and daughter of Simon Sallard and his wife, Elizabeth Tayor, daughter of John Taylor, "ancient planter".
So, She was born Mary Sallard, first hunsband was John Kelly, second husband Henry Lawson by 1709.
I will try to help with her bio and the merging of the Sallards.