Hers and Welles' first project together, which began filming in 1967, was The Deep (1970) starring Jeanne Moreau and Laurence Harvey. It was abandoned in 1969 and left unfinished - one of the couple's many projects that fell through.
Oja never became the fourth Mrs. Welles. A year after Orson's death, the third Mrs. Welles (actress Paola Mori) and Oja finally agreed on the settling of his will. On the way to their meeting to sign the papers, however, Mrs. Welles was killed in a car accident.
Around 1969, in a Charles Foster Kane/Susan Alexander like move, Welles renamed Olga "Oja Kodar" and started building her up Svengali-style to become a big star. As in Citizen Kane (1941), it didn't work.
Member of the jury at the Venice Film Festival in 1991.
In 1970, an Italian newspaper published an exposé of Welles' affair with Oja. Welles, who was editing the movie Don Quixote (1992) for more than a year with editor Mauro Bonanni, angrily left Italy forever to return to America, and Quixote was never finished.