In the mid-1980s, she reduced her film appearences in order to pursue other activities.

In the theatre she worked with Fiorenzo Fiorentini, in the comedies Morto un Papa se ne fa un Altro, Strega Roma and Chicchignola written by Ettore Petrolini. All were directed by Ghigo De Chiara and Fiorenzo Fiorentini

In addition, De Santis appeared in Sottoveste by Castellacci e Ventimiglia and Love and Life by Mike Immordino.She wrote and acted in La Bambola Orchidea which also featured the music of maestro Aldo Saitto.She was in a repeat engagement of Chicchignola with Mario Scaccia.

In 1998 and 1999 she worked in the comedy La cicogna si diverte by Carlo Alighero.