I'll temper the above advice a bit. Don't sue over $250 or $500 in deductibles. Take action only after you have several things accumulated. However, there is no reason why you should NOT be building your case.
In Texas, payment of medical expenses, including each parent's share of med out of pockets, is considered child support. Meaning it is very enforceable, and she would have to pay part of your legal fees if found in violation of orders.
You should insist, in brief, professional business like letters, sent via certified mail return receipt requested with a copy by another means (like email or fax), that she pay the bills. You should be very specific as to the amounts she owes and to which providers. Give her specific time periods (like 10 days) to pay the bills. Make sure your terms are consistent with orders -- as in she is required to have paid them already so the 10 days serves as an additional reminder.
Do not pay until after she has received this letter and the ten days has passed.
Then, if after a certain period, you've accumulated alot of bills, add them up, then approach her again. If she ahs accumulated any bills, net out the two.
You pursue a Motion to Enforce when this amount is large enough to warrant it. Hopefully she'll have seen the light by then. Or if you have anything else to chase, you chase it, as use the Motion to Enforce as leverage.
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