By Barbara Liston

ORLANDO, Fla (Reuters) - The estranged daughter of Oscar-winning actor Billy Bob Thornton was sentenced in Florida on Thursday to 20 years in prison for killing a child in her care.

Amanda Brumfield, 32, was convicted in Orlando in May of aggravated manslaughter of a child in the death of Olivia Madison Garcia, the 1-year-old daughter of one of Brumfield's close friends.

The child's mother, Heather Murphy, said after the sentencing that she was surprised at how long a prison term Brumfield received, but that it meant little to her.

"None of it satisfies me. It doesn't matter ... I won't ever see Olivia again," Murphy told reporters.

Brumfield contended at trial that Olivia fell out of her playpen and hit her head in October 2008, but prosecutors argued the child's skull fracture and brain bleeding were no accident.

The jury acquitted Brumfield of first-degree murder and aggravated child abuse charges.

Brumfield's relationship with her father became a topic of media interest after her arrest in 2009. Thornton won an Academy Award for best adapted screenplay for the independent film Sling Blade, for which he also was nominated for a best actor award.

Thornton has wed five times, including a failed marriage to actress Angelina Jolie, and has four children by three women. Amanda was the product of his first marriage in 1978 to a woman from his home state of Arkansas, according to a 1997 profile of Thornton in People magazine.

In 2005, Thornton, speaking of Amanda, told the U.K.'s Mail on Sunday, "She didn't grow up with me, and so we were pretty much strangers for years. Then a few years later, we reconnected, and it's really good now."

But after Brumfield's arrest, Thornton's publicist, Arnold Robinson, told CNN that the actor was estranged from his daughter "and has had no contact with her for quite some time."

(Editing by Colleen Jenkins and Cynthia Johnston)