Together with her friend, actress Beatrice Cole, Susann wrote a play called The Temporary Mrs. Smith, a comedy about a one-time movie actress whose former husbands interfere with her scheme to marry a man of wealth. Retitled Lovely Me, the play, directed by actress Jessie Royce Landis, and starring Luba Malina and Mischa Auer, opened on Broadway at the Adelphi Theatre on December 25, 1946. Said to be an "audience-pleaser," the play nonetheless closed after just 37 performances. Four years later, Susann and Cole wrote another play, Cock of the Walk, which was to open on Broadway with Oscar-winning actor James Dunn. For reasons which remain unclear, the play was not produced.
On December 6, 1946, Susann gave birth to their only child, a son whom they named Guy Hildy Mansfield, "Hildy" being for cabaret singer Hildegarde, who was the boy's godmother. At the age of three, Guy was diagnosed as severely autistic, and eventually had to be institutionalized; Susann and Mansfield did not reveal the true reason for his absence from home, fearing that he would be stigmatized should he eventually recover. Reportedly, Susann and Mansfield rarely missed a week visiting their son.