2001 Dodge Intrepid Catalytic Converter

My 18 yr old daughter bought her 1st car 10 months ago (Dec 07). After approximately 1 month her check engine light went on so she brought it back to the used car dealer. He told her it was her catalytic converter and that they replaced it. The car had 52K miles at the time. The check engine light has now come back on and the diagnostic says it is the catalytic converter. I've heard rumor catalytic converters are covered by warranty up to 80K miles. What should my daughter do? I also understand the cat is used only for emissions, so will it hurt the engine if she doesn't get it replaced? Of course the dealer will not fix the car because it is now past the 30 day warranty. She is a full time student and work as a server part time, she can't afford to have the cat replaced. Please give us some guidance!

Thanks,
Maggie Pagels