[8] While modelling in Los Angeles and making uncredited appearances in films, she was chosen for a small role in the wartime B-movie melodrama Parachute Nurse (1942).

The other newly contracted players featured in addition to Riordan included Lon McCallister, Margaret Early, Sunset Carson (as Michael Harrison) and Cheryl Walker, a former “stand-in” for actresses Veronica Lake, Claudette Colbert and Madeleine Carroll.

[12] Shortly afterwards, Riordan's contract was transferred from Sol Lesser Productions to Warner Bros.[13] where she was cast as Bette Davis's daughter Fanny Jr. in Mr. Skeffington (1944).

[19] She also assisted in the fundraising efforts that were part of the joint Navy and Red Cross campaign to sell war bonds to help raise money that would go towards building the cruiser USS Los Angeles.

[20] The wartime effort activities she participated in along with the increased visibility that the film Stage Door Canteen had brought, and her modelling experience,[4] lead her to also be promoted as a pin-up beauty[21] among G.Is.