Born in Philadelphia, Pennsylvania, MacWatters studied at the Curtis Institute of Music, and sang 611 Broadway performances of Adele in Rosalinda (an adaptation of Die Fledermaus), conducted by Erich Korngold, from 1942 to 1944. She made her formal operatic debut at the San Francisco Opera, as Musetta in La bohème, in 1944.
The soprano also appeared on Broadway in La serva padrona (as Serpina, 1944) and Mr Strauss Goes to Boston (as Brook Whitney, 1945). MacWatters sang at the New York City Opera from 1946 to 1951, in The Pirates of Penzance (as Mabel, conducted by Julius Rudel), Rigoletto (as Gilda, with Giuseppe Valdengo and Luigi Infantino), Il barbiere di Siviglia (as Rosina, opposite Enzo Mascherini), The Old Maid and the Thief (as Laetitia, with Marie Powers), Le nozze di Figaro (as Susanna), Les contes d'Hoffmann (as Olympia), and Ariadne auf Naxos (as Zerbinetta).
MacWatters appeared at the first season of opera in English at Covent Garden following World War II, in the name part of Manon and as Sophie in Der Rosenkavalier, in 1947. At the New Orleans Opera Association, the coloratura was seen in Il barbiere di Siviglia (1949), Die Fledermaus (1955) and Le nozze di Figaro (opposite Norman Treigle in the title role, 1956).
For the Metropolitan Opera, she played Adele in the national tour of Garson Kanin's production of Die Fledermaus, from 1951 to 1952. MacWatters's house debut was also as Adele, with Regina Resnik, and, later, Eleanor Steber, as Rosalinde von Eisenstein. From 1953 to 1955, she was also heard there in La bohème, opposite Victoria de los Ángeles as Mimì. She returned to the Met in 1957, for Fiakermilli in Arabella, with Lisa della Casa conducted by Erich Leinsdorf.
MacWatters became Artist in Residence at Indiana University in 1957, and remained on the voice faculty until her 1982 retirement. She died in Bloomington, Indiana, at the age of ninety-three.
- "Obituaries," Opera News, June 2006.