Doesn't your state have a CS calculator? This is how most states do it, to ensure there is nothing other than the facts involved in the CS amount and who pays who. It is all just a formula based on incomes, expenses and amount of time spent with each parent. In our state, you cannot change the amount set by the calculator at all - - so if your state is the same, then she needs to accept that this isn't about whether you are trying to "make her pay", its about an impersonal formula and is not even your decision. If the formula says she has to pay you, then she has to pay you, and that is that.
I hope for your sake your state uses such a formula, so that you can take away from her the idea that it is your fault or plan to "make her pay".
