Leatherman was facing her first glimpse of freedom since March, when she was arrested outside Cusack's home. She indicated during the hearing that she felt jail was making her sick and that she wanted to leave.
She faces four years in state prison if convicted.
Cusack, star of such films as "Being John Malkovich," "High Fidelity" and "Grace is Gone," is expected to testify during the trial.
On Wednesday, Leatherman appeared in court and was subdued at first, answering a prosecutor's questions simply and politely.
Her demeanor was drastically different from an August court hearing, during which Leatherman berated Judge Susan M. Speer. The judge had just found her competent to stand trial, but not to act as her own attorney.
But during Wednesday's hearing she accused her attorney, Brent Merritt, of using scare tactics to get her to agree to the deal. Merritt, who was appointed against Leatherman's wishes, denied the allegation in court.
Leatherman seemed unsure of the agreement at times, prompting a prosecutor to ask repeatedly her whether she wanted to accept the deal.
Her uncertainty led Speer to discard the deal and order jury selection to begin Friday morning, causing Leatherman to express a willingness to accept the plea deal.
"I want to take it," Leatherman shouted before bailiffs led her off in handcuffs.