She can try to modify custody, but Georgia now considers moving out of state to be a major change in circumstance. Thus, you can seek primary custody of your children and request that they remain with you. I would highly recommend you seeking an attorney to assist you in this matter as soon as possible.

If you truly have joint physical custody (not just joint legal custody), than she cannot move because she will be in contempt of court. If you have a schedule that gives you 50% of the time with the children, or close to it, you have a very good chance at preventing the children from moving. (She can always move, but the court can stop the children from going with her) How involved have you been? Have you missed or canceled parenting time, or, have you been an active father in their lives? The real answer to if she will be able to move is up to you. We have handled many fathers' rights cases like this in the past, and have been successful in either gaining custody for the father in these situations or convincing the mother not to move in order to avoid an expensive court battle. There is more information on my website, www.georgiafathersrights.com.