As a U.S. citizen over the age of 21, you can sponsor your mother for a green card. Depending on how long she was in the U.S., she may be subject to a ten-year bar to returning to the U.S. Since she left with voluntary departure rather than a deportation, she will not need a waiver for a deportation. You need to review her circumstances with an experienced immigration attorney before you file the I-130.
Good luck,
Mark
Answered on Feb 15th, 2012 at 2:34 PM