Victoria pretty much said it. I know in CT there also has to be 20% change in what the support would be for the courts to even entertain it. Also, if you two have a child together and the ex is going for more support then your child would now be thrown into the mix as you now have the expense for that child as well.
My husband tried to "play nice" with his ex wife for the benefit of his daughter and he would give and give and give (above and beyond). Eventually she got very greedy (and the daughter wasn't getting the benefit). He went to court, had everything adjusted (it worked in his benefit) and now he pays what is required. He has lives in the same state and has visitation, so it's a little different.
Good luck. Greedy ex wives can be a handful, but go through the courts. I'd like to know where she's going to get the money to pay for an attorney if she's not working. The child support is supposed to be for the child, not her, so maybe she should get a job.
Also, I believe you will have to go through the court where the divorce was finalized. So if they got divorced in NJ, she'd have to fight the issue in that court.