She starred in 's short-lived 1982 prime time soap opera and played the lead female role on the 1984 television series.
When she was only eight years old, she was seen in her first television commercial.
O'Neill has dual citizenship, being a Brazilian and American citizen.
She made guest appearances in the series like 90210, Beverly Hills.
Afterward, she appeared in several films include Molly, Saving Sarah Cain, The Man Who Came Back, Point Doom, Black Widow, and others.
In the early years of 2005, she and Mark Platzer welcomed a son whom they named Logan.