Consult an attorney regarding filing the affidavit of support. It involves too much detail to be discussed based on the facts you provided.
3. Obtain assistance from an immigration attorney
IF she does not live with you, no need to include her as a household member. She needs to file I864
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.
Yes. I-864 and the same financial documents as the promary sponsor.
A household member is someone that lives in the same household as you.