You have to file a Petition for Modification.
By "Prove Up", she probably means she wants the judge to hear the case.
Some courts require that you file a Financial Disclosure Statement.
If your income has decreased, you need to file a motion to modify child support. The sooner you do it the better as your support will be modified effective the date you serve notice of your motion on you ex. While you can try to accomplish this yourself, you are much better of hiring an attorney to help you. You are fortunate that here are many good lawyers in your area. Speak to one o more and hire the one you like best.
Your ex wanting to "prove up" does not make sense. Speak to your lawyer about that.
if you have a lawyer contact her. You need to file a Motion to Modify. It is not clear if this is temporary support or not. A prove up is what is done at the end of a divorce case to make your agreement final in court before the judgment is signed by the court.
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