What did Secretary of Treasury Janet Yellen say about crypto?

Could you elaborate on Secretary of the Treasury Janet Yellen's views on cryptocurrency? In her statements and public appearances, has she expressed concerns or support for the digital asset class? Did she mention any specific measures or policies the Treasury Department may be considering to regulate or monitor cryptocurrencies? Has she discussed how the crypto market could potentially impact financial stability or economic growth? It would be interesting to understand her perspective as a key figure in U.S. fiscal policy.