If you are here on an F-1 visa she can apply for an F-2 as your dependent as long as you can prove she is your wife and she can overcome the suspicion from the Embassy/Consulate that she will not fail to depart the US when you are done with your studies. If she wants to apply for an F-1 visa then she just needs to follow the same steps as you did.
You are confused and need a consultation with an immigration attorney.
NYC EXPERIENCED IMMIGRATION ATTORNEYS www.myattorneyusa.com; email: firstname.lastname@example.org; Phone: (866) 456-8654; Fax: 212-964-0440; Cell: 212-202-0325. The information contained in this answer is provided for informational purposes only, and should not be construed as legal advice on any subject matter.
I agree with both of my colleagues. Your wife may qualify for an F2. There may also be other alternatives and a consultation with an experienced immigration attorney is advised.