H. Coleman who was only at the school in late 1818, right before the school was sold.*(It turns out that H. Coleman is really Maria Coleman again--see below.)
Louisiana Coleman, of Richmond VA, who attended for both sessions of 1817 and may have had a "John W. Pleasants" attached to her account.
Margaret M. Coleman attended both sessions of 1813, and was connected to a Col. H. E. Coleman.
Maria Coleman attended for six sessions, mid-1815 through mid-1818, and was also connected to a Col. H. E. Coleman.
The main mentions of these Colemans in the Mordecai papers seems to be in the ledger: Col. Coleman paying for music and French in July 1813 (so that's for Margaret), "John W. Pleasants for Miss Coleman" in January 1817 (so that's Louisiana), "Col H E Coleman, Miss Maria" in January 1818, etc. There was a bill paid to a shoemaker, for boots for a group of girls including "M Coleman," in March 1818. The family also knew a Dr. Coleman in Warrenton, who may have been kin to these girls, but there are no mentions of daughters or nieces of his at the school.
Louisiana Coleman's unusual first name makes her a good place to start. Louisiana Coleman (1804-1883) was the youngest daughter of Maj. Samuel Coleman (1755-1811) and Susannah Pleasants Storrs, of Henrico County, Virginia. Her unusual first name was part of her family's pattern--she had among her older sisters "Araminta" and "Emmeline." Her father died in 1811, so the John W. Pleasants who covered her bills might have been a maternal relative. She married John Newton Gordon (1793-1870) in 1823, and they had eight children who all lived to adulthood: Susanna, James, Amelia, Mary, Maria, Ann, John, and Edward (guess she didn't inherit her parents' fancy for offbeat names.)
Col. Henry Embry Coleman (1768-1837) turns out to have been a prominent figure. Among other roles, he was on the jury that tried Aaron Burr for treason in Richmond in 1807. His house, Woodlawn, was in Halifax County on the Staunton River, near John Randolph's plantation. He and Anne "Nancy" Gordon (d. 1824; not a sister to the John Newton Gordon above, but maybe not a distant relative either) married in 1795, had twelve children; their eldest daughter Elizabeth married Charles Baskerville, whose sisters Mary and Ann Baskerville attended the Mordecai school.
Second daughter Margaret Murray Coleman (1798-1869) was probably the Mordecai student Margaret M. Coleman. She was fourteen when she arrived at the Mordecai school for a year of education. She married in 1821 to Richard Logan (1792-1869) of Halifax County, a lawyer and member of the Virginia legislature. They had seven children; Margaret's son Richard died at Gettysburg. She died just six months after becoming a widow, and is buried in Halifax County.
Henrietta Maria Coleman was the fifth child, third daughter in the family--so "H. Coleman" and "Maria Coleman" in the rolls were, indeed, very likely the same person. She was born 1803, attended the school from 1815-1818 (ages 11-15), and married in 1834, to Rev. John Thomas Clark of Halifax County. They lived at Chester VA (this house seems to have been Rev. John's), and had three children. She died in 1844, age 40.