Prosecutors say the 32-year-old was convicted last Friday.
Brumfield was accused of killing her best friend's daughter while babysitting for an overnight stay in October 2008.
Brumfield said the child was trying to climb out of a playpen and hit her head, and the defense argued the fall may have caused her death by aggravating a previous injury.
Prosecutors shot down the claims, saying it's impossible for a fall from that height to cause a 3.5-inch fracture on the girl's skull and the bleeding and swelling found in her brain.
Brumfield was acquitted of first-degree murder and aggravated child-abuse charges. She is expected to be sentenced in July.
(Originally published June 1, 2011, at 7:07 p.m. PT)