Could this be our Mary?
Mary Bagley [1760.1.4.4.1] was to be the bride of Matthew Cox who got a marriage bond to marry her from Amelia County 21 November (bond) 1764. James Bagley was his security and her father consented to their marriage. Yet four months later, on 25 March (bond) 1765 , Mary Bagley married Richard Ligon [3520.3.1.3.2]. Perhaps Matthew Cox did not live long, yet no will for him is in Amelia County. Or possibly the bride simply changed her mind and declined to become Mrs. Cox.