There's a student named Marion Galloway in the list of Mordecai school students I compiled in the 1990s. She may have been from Halifax County, North Carolina, attended the school from the beginning of 1817 to the end of 1818, and a Robert Galloway is the adult name attached to her account. Not much to go on, but let's see how much more we can learn about her now...
One thought: Marion is not a very common name for the students at the Mordecai school. Mary, Mary Ann, sure, but I don't see other Marions in the list. So I'll definitely check other spellings.
Here's one potential match: Marion Galloway, daughter of Robert Galloway and Mary Spraggins Galloway; her father was a Scottish immigrant and died in 1832. He lived in Rockingham County NC, owned a tavern at Wentworth, and in the 1820 census there are 77 enslaved people recorded at his plantation. In his will, her name is clearly written "Marion" (see snippet from Ancestry). And she is listed as the wife of James E. Galloway--so she may have married a cousin, or otherwise landed with a matching maiden name and married name. She and her husband were given land in Tennessee, and a dozen enslaved people, in her father's will.
Her husband died in 1833, in Maury, Tennessee, leaving her a young widow with a young daughter, Cornelia, and son, James A. Galloway. James E. Galloway's will is also on Ancestry; here's where she's named ("my dearly beloved wife Marion Galloway"), along with her two children. Her brothers-in-law, Samuel W. Gentry and Reuben A. Gentry, were the will's executors.
The timing, name, class, and locations match up fine; this very well could be a Mordecai student. But I don't have quite enough to feel like this is a definite match.