You have not provided sufficient information to evaluate your case. Are you a U.S. citizen? Have you already filed the green card application for her? If you are US citizen and you are planning to file the Adjustment of Status application for her, then typically once her visa expires, Immigration will allow her to remain in the U.S. while they adjudicate your application. However, she does not really have a specific legal immigration status during this time (such as now she has valid F1 student status). Because she will likely be going out of status before any interview could occur on your application, you should review your green card paperwork with an attorney before filing. Or consider hiring an attorney to represent you and prepare the application. That way you can be assured that you are filing all of the correct paperwork. It is not just one form - it usually involves around 6 to 7 different forms plus documentary evidence so it all ends up being a thick packet. But if not done correctly you are at risk that Immigration would deny the application and since her status had expired, she could be put into deportation proceedings. If you do not wish to hire an attorney, then I would at least recommend that you carefully review the USCIS website and download and prepare all of the forms the best you can and then at least schedule a consultation with an immigration attorney to review them before filing.