She has deep brown eyes and short, curly, black hair.
She is first introduced in the episode "Touched by an 'A'-ngel." Kate introduces her to Hanna and Mona at the West Maple Riding Club along with Elizabeth. Her name is pronounced "Mar-go" due to the silent "x," as is common in French transliterations. Mona asks Margaux (in French) about her name's origin, and she responds (also in French) that her family is originally from France, though does not specify if she was born in France or the United States. At the end of their riding day, Hanna inadvertently insults Kate, Margaux, and Elizabeth within their earshot when a microphone on Mona's helmet is "accidently" activated without Hanna knowing. Hanna feels that they had been nasty towards her, as they had been giving her the cold shoulder, but the friends all gasp in apparent surprise. She follows Kate in leaving when Hanna tries to apologize.