Margaret was a girlfriend of Jerry Seinfeld and (believe it or not) Newman. She only appeared once, in “The Big Salad”. She was played by Marita Geraghty.
Newman dumped her because “she wasn’t my type.” Jerry was very attracted to Margaret, yet he could not get over the fact that she was dumped by Newman, and not the other way around. The two soon broke up soon after Jerry learned of her past with Newman and was unable to cope with it; in Jerry's own words, "Newman found this unacceptable!"