The cause of Bartusiak's death wasn't known, but she had recently been having epileptic seizures, her mother said.
The woman's boyfriend found her dead in her bed at her Texas home.
"We think she had a seizure and choked and nobody was there," Helen McCole Bartusiak, the actress' mother, told CNN.
"We lost our girl. She was a kind and really beautiful girl," she added.
Bartusiak had roles in The Cider House Rules, Don't Say a Word and Sick Boy. Most recently she was preparing to produce and director her first feature film, her mother said.
Actress Abigail Breslin, a friend of Bertusiak's, expressed her grief at the passing on Twitter.
One of my very good friends and someone who was like a sister to me, Skye McCole Bartusiak passed away today. So devastated.— Abigail Breslin (@yoabbaabba) July 20, 2014