"Today I am free," UsMagazine.com reported Schrader told reporters at the Venice Film Festival Friday. "In the past 16 months, I have been hostage to Lindsay Lohan. She is a great actress, she should be here, but her behavior is unspeakable."
"Yes, nobody thought it was a good idea for her to go," a source told the magazine about Lohan's absence from the film's screening at the festival. "That sort of atmosphere, the festival, the parties. The culture of it is drinking and celebration and not in line with keeping her on the right track."
Lohan, 27, recently completed a 90-day, court-ordered rehab stay.
The actress was under court order to undergo in-patient treatment for substance abuse as part of her conviction for reckless driving and lying to police.
She checked into the Betty Ford Center May 3 but was reported to be unhappy with her treatment and requested a transfer to Cliffside Malibu. She wrapped up her treatment and left the facility last month.
The "Mean Girls" and "Freaky Friday" star's once-bright career has been eclipsed by her battles with drug and alcohol addiction, motor vehicle offenses and other legal woes.
The Oprah Winfrey Network was reported to have paid the troubled actress about $2 million to star in an eight-part docu-series about her efforts to remain sober and revive her career.