Denise Fergus had accused the makers of Detainment, which centres around the police interviews of James's killers, of being “obsessed” with the case.
She had demanded they remove the film from contention at the Academy Awards after it was nominated in the category of best live action short, a request director Vincent Lambe refused.
After Detainment was beaten on Sunday by biographical drama Skin, Ms Fergus tweeted to say she was relieved.
She said: “I'm so made up, that short film Detainment did not win the Oscar, can't tell you just how relieved I am, thanks to everyone who has agreed with me on this xx.”
They led him to a railway line before killing him. Venables and Thompson were convicted of murder and have since been given new identities.