The conventional reading of the Winkie's diner scene is that Diane pays Joe to arrange Camilla's murder. But what if that money is a bribe — an attempt to influence Camilla's casting in a film — rather than a contract killing?
The Winkie's scene takes place before the dinner party, not after. Diane's breaking point comes not from deciding to kill Camilla at the party, but from realising that the woman she loved and financially supported has betrayed her. Diane had invested in Camilla's career; Camilla achieved success through other means — another director, or Adam Kesher — making Diane's sacrifice both futile and, ironically, a factor in losing her.
Diane's suicide, on this reading, stems from three converging losses: a love affair ended, a Hollywood career that went nowhere, and the humiliation of watching Camilla flourish with someone else. The packed boxes in her apartment suggest she is preparing to leave the industry altogether.
In Diane's dream, the blonde Camilla is forced upon director Kesher by the mob. This may be a distorted reflection of reality: Diane's money — not talent alone — is what originally secured Camilla's casting. The original arrangement may have been mutual career advancement, with Diane expecting to ride Camilla's coattails into success. When that arrangement collapsed, so did everything else.
Problems with this interpretation
Why would Diane sacrifice her own career aspirations purely for Camilla's benefit? And if Joe is merely a fixer for casting deals, the film's suggestion that he is a genuinely dangerous man — capable of multiple murders — sits uneasily with such a mundane role. These are real weaknesses that the theory does not fully resolve.