If it does get to court, white out all your info (ss # and salary) and white out the total amount you make. Have him bring his last two paystubs. This way she does not get your info at all. The judge had no problem with that, my husband told judge that I was not a party of the case and my info was whited out. My state it is a simple formula of the NCP (dad) salary so really the mother's salary does not come into play too much here.
She probably did not do it before because she would have to go back to original state to deal with this. If she
moved out of that state, she would have to live there over 6 months and ask new state to take over which would stop her
child support for a few weeks/months until new state go the paperwork in order.
What does the order say about Christmas break? If it says you get child this year, then use the letter of intent from this site. It is very good and states you intend to have child. If she does not send him, you can file a contempt of court papers and have her tell a judge why is she not following the
court order. You could ask for make-up time in those papers and lawyer fees as she is going against a court order.