She can file the petition for her spouse. However, if and when the spouse files an application for Adjustment of Status in the U.S. or goes through Consular Processing for an immigrant visa abroad, he would have to submit an Affidavit of Support from her. To file the Affidavit of Support, she must be at least 18 years old. So even though she can file the petition now, she would have to wait until she is 18 to file the Affidavit of Support (which should be fine, since the Petition would take about that long to be approved).
Answered on Sep 20th, 2013 at 12:54 PM