"Unfortunately (the Manson movie) didn't come together quickly enough, and she was offered other roles, which she accepted and is looking forward to doing," Sloane told Reuters.

The ABC television network announced on Monday that Lohan, who is seeking to rebuild her career after a year of personal upheaval, has signed a deal to guest star in six upcoming episodes of the popular workplace comedy "Ugly Betty," starting this month.

Sloane said Lohan also has been cast to star in the forthcoming film comedy "Labor Pains," produced by Rick Schwartz, whose credits include the Martin Scorsese films "The Departed," "The Aviator" and "Gangs of New York."

As described in the New York Post, Lohan will play a young woman who pretends to be pregnant to avoid being fired.

For "The Manson Girls," Lohan had reportedly been attached to play a Manson "family" cult member named Nancy Pitman.

But a source with knowledge of the project said producers failed to put money into escrow in time to hold Lohan's availability, leaving her free to take other work.

Manson, now 73, was convicted of masterminding the grisly 1969 killings of Hollywood actress Sharon Tate -- the pregnant wife of film director Roman Polanski -- and six other people during a two-day rampage in the Los Angeles area.

Originally sentenced to death for ordering his followers to carry out the mass killings, he is now serving a life sentence at the Corcoran State Prison in California.

Lohan has not starred in a feature film since last year's flop "I Know Who Killed Me."

She spent much of 2007 out of the public spotlight after she was arrested twice in one month for drunken driving and re-entered rehab in a relapse of substance abuse that cost her a role in a film produced by and starring Oscar winner Shirley MacLaine.

The year before, a studio executive publicly rebuked Lohan for repeatedly showing up late on the set of "Georgia Rule," which he blamed on her late-night clubbing habits.