The crossword solution for the term 'Sweetheart of Sigma Chi' is COED, which stands for a female student at a coeducational college or university. Coeducational institutions are those that accept both male and female students, and the Sweetheart of Sigma Chi is a woman who is chosen to represent the fraternity. She is typically an active member of the fraternity and is expected to serve as an ambassador for the organization.