You should research the LaMusga case that was recently heard in California. That will give you an idea on how the California courts are looking at CP's moving away.
You say she "just" obtained the wage garnishment. How recently was this? Was there a hearing? If so, did you go to it and offer your defense?
Or, is this an old order that she just now took back to court to get the garnishment? If this is the case, why didn't you already file for a...
If everything was issued in Georgia and the child and one parent still reside in Georgia, then Georgia is the state with continuing, exclusive jurisdiction.
That said, you need to read O.C.G.A. 19-7-54. Here is the link for it...