Elizabeth Martin is the daughter of Mrs. Martin and the sister of Robert Martin and an unnamed other sister. She befriended Harriet Smith while attending Mrs. Goddard's school, and she invited her to spend two months at Abbey Mill Farm with her family. She supports her brother's relationship with Harriet. She shuns Harriet after her call on Abbey Mill Farm and she rejects Robert, to the point that she initially pretends not to see Harriet when they are all at Ford's.
She calls on Harriet at Mrs. Goddard's, and when she is not there, she leaves a prepared note. Emma Woodhouse agrees that Harriet must return the visit, but she brings her in her carriage and calls again so soon that Harriet cannot properly renew the acquaintance.
Months later, Harriet accepts Robert's second proposal, and they are married before the end of September. Harriet spends more and more time with the Martins during her engagement, causing her friendship with Emma to cool.