What language does the film "Nell" explore, and how does it portray the idea of language isolation?

"Nell" follows the life of a woman named Nell, played by Jodie Foster, who has been raised in a remote cabin in the woods by her mother, who suffered a stroke and had difficulty speaking. After her mother's death, Nell is discovered by a doctor named Jerome Lovell (Liam Neeson) and a psychologist named Paula Olsen (Natasha Richardson). Upon interacting with Nell, it becomes apparent that her language is a unique combination of English and a private vocabulary that she invented with her late twin sister as children.