Will getting married affect her immigration status?

If your intended's mother only has a green card and filed for her under the F-2B category as the single son or daughter of a permanent resident, her getting married to you would destroy the petition. If her mother is a US citizen, the marriage would change her petition category from F-1 (single son or daughter of a US citizen) to F-3 (married son or daughter of a US citizen). That being said, your marrying her in a bona fide marriage would probably be her best step as she entered the country legally and would be eligible to adjust status approximately 5 to 9 months after your papers are filed for her immigration. Unless she has maintained legal nonimmigrant status or has the benefit of section 245 (i), she would not be eligible to adjust status under her mother's petition when it becomes current and would have to seek consular processing. I do note that with the President's executive action of November 20, 2014, a person in her situation should be able to apply for and see the result of an I-601A provisional waiver application prior to deciding to complete her mother's immigration petition in a consular interview overseas. Due to the limitations of the Lawyers.com Forums, Alan Lee, Esq.'s (the "Firm") participation in responding to questions posted herein does not constitute legal advice, nor legal representation of the person or entity posting a question. No Attorney/Client relationship is or shall be construed to be created hereby. The information provided herein by the Firm is general, and requires that the poster obtain specific legal advice from an attorney. The poster shall not rely upon the information provided herein as legal advice nor as the basis for making any decisions of legal consequence.