You need to figure out the impact on your relationship. I would at least fight her if you are going to be concerned about the loss of your child. However, it seems like you are a little upset...me, I would go down fighting to the bitter end. Just b/c it is for a better job does not mean it is better for the child.
If you want to fight it you need to hire a lawyer. File for a motion to block the move. Ask for custody. If she relocates she more than likely will be responsible for most of the traveol costs.
Read the FAQ section to the left...move aways are hard. I know my mom moved me from my dad when I was a child. Haven't seen, heard from him since.
So, pick your battles. This is one worth fighting.