Generally speaking a person who is "unlawfully present" in the U.S. for a year or more is inadmissible for 10 years. If your friend remained in the U.S. for 4 years beyond the date her form I-94 expired then she is almost certainly is inadmissible for 10 year from the date of departure although she must consult with an immigration attorney to be certain. Nevertheless, she may apply for a visa at the consulate and if the application is refused because of the 10 year bar she may request a waiver.
PROFESSOR OF IMMIGRATION LAW for over 10 years -- This blog posting is offered for informational purposes only. It does not constitute an attorney-client relationship. Also, keep in mind that this is an INTERNET BLOG. You should not rely on anything you read here to make decisions which impact on your life. Meet with an attorney, via Skype, or in person, to obtain competent personal and professional guidance.