You need to contact the Florida Department of Revenue Child Support Enforcement Unit.  They are the ones that will help you collect the money owed to you.  You can indeed get a judgement against her for the back money owed ("arrears") and then "execute" on the judgement. That could definitely include having the Sheriff or Marshall seize the vehicle.  I would go down and file the child support order and speak with someone on how to make sure that you are paid on a regular basis.  And if you have a judgement then it is enforceable even as against her estate in the event of her death.  So do whatever you need to do.  Good luck.