If you are required to report fraud, then of course make a report. Privately.

Talking about it in the open when others could hear is a different story. Or keep pushing it by calling her a crook. Make a report and let them deal with it

If you already reported it, then you can’t be liable as you addressed it. The fact that they do nothing about it or aren’t firing her isn’t your business really. If you continue talking about it, you will be seen as the one causing problems.

Now if you feel you are forced to commit fraud or crime despite you making reports about it, perhaps you should look for a different job.