You have not given sufficient information necessary to answer your question. A petition may be approved but, unless that petition is current in its visa category, you cannot apply for adjustment of status [assuming you are physically in the US], nor can you apply for an immigrant visa at the US post overseas. To know for sure if your approved petition is now current, you must give information about your specifics visa category. This depends amongst other things, on your age, and marital status and your country of birth when your mother filed the petition, such information not having changed since.
Answered on Feb 26th, 2013 at 2:40 PM