First, no, it's not fair that the hearing goes forward without you but is rescheduled if she's not there, but it is legal. Because the money is for the child, not the parent, it wouldn't be considered fair for a child to have to be not supported because his mother missed a hearing. So, the state will continue the case because their focus is on doing what's best for the child.
As far as support itself goes, in Texas, support is based on the father's income and the number of children. The mother's income doesn't come into play at all, so she shouldn't get any extra just because she's not working. Take a look at this calculator to see what you might be obligated to owe.
If she tries to claim that she needs a deviation from the amount provided by that calculator because she's not working, then you can argue that she should ALSO be required to work to support her child and that you should not have to pay extra because of her refusal to work. As long as you never signed something promising to support her, the law is on your side. Not working is a luxury, not a right, and she doesn't have any right to make you support her in addition the child if you were never married.
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