She does not have to leave US after your marriage, and certainly it is unadvisable for her to leave the US once her Form I-485 is filed. Properly done, she will receive notice of her Biometrics [fingerprint] interview within a month of filing and her EAD work permit follows no later than 90 days after filing; you will be scheduled for green card interview within 6-8 months. Her departure from US after filing her I-485 application is deemed an abandonment of her case and she may be refused admission to the US once she departs. It does not appear you are aware of the issues and I strongly suggest that you consult with an immigration lawyer so you avoid some of the possible minefields in this matter.
Answered on Mar 21st, 2013 at 4:39 AM