Legal Question in Family Law in California

The only way to retroactively change an order like that is if there was actual and intentional fraud by the other party. The mere fact that they over-estimated her income, or the evidence they presented made it look like her income was higher than it was is not grounds to go back and retroactively modify anything. New evidence is most certainly not grounds to modify it more than a few weeks after it was entered, and only then if there is clear proof that the evidence could not have been submitted at the time of the hearing. If her income is still lower than what the order was based on, she can file a motion for modification of support, but the order lowering the support will only be retroactive to the date she files the motion for modification. So the sooner she files the better.