She began singing in her brother's band in Washington, D.C., then was featured in Artie Shaw's band after Billie Holiday left in 1938. Forrest joined Benny Goodman when Shaw disbanded in 1939, staying until 1941. She recorded with Nat King Cole's trio and Lionel Hampton in 1940, then began to score hits working with the Harry James orchestra. During the early '40s, she had string of successes. Later she teamed with Dick Haymes on his radio show and on six duets that were big hits. Forrest cut back her activity in the '50s, then sang with Tommy Dorsey's Orchestra led by Sam Donahue in the early '60s. She continued to work on the club circuit in the '70s and '80s, making a new album for Stash in 1983. Forrest died July 11, 1999 at age 82.