I can't confirm that the Mary Allard found in the 1830 census for Crawford Co., Arkansas is Mary Burleson who married David Allard circa 1799...BUT, I stongly suspect that it is she because her daughter, Lucy (my GGG Grandmother) married Benjamin Pigman between 1830 and 1835 in Northwest Arkansas. Benjamin and Lucy's first child, Nancy, was born in Arkansas around 1835.
Benjamin is first found in the Washington Co., Arkansas tax list in 1836. Washington and Crawford counties are adjacent. Later, the Pigmans are found in Madison Co. which was formed in part from Washington Co.
So far, I have not been able to determine what might have happened to Mary Allard after 1830.
As an interesting aside, in his last years Lucy's brother, Aaron Hardin Allard married another of my GGG Grandmothers in 1864 in Hopkins Co., Texas. Her name was Hazy Garrard and her daughter Frances married Martin Pigman, son of Benjamin and Lucy.