Well....actually.....she was a spectacular failure.
...What if I told you that our government is unintentionally completing a criminal conspiracy to deliver Central American teens from cartels and smugglers to other illegal aliens, resettling them on our dime, and sending them to our schools, all the while enriching some of the most evil organizations and nourishing the growth of MS-13 and drug traffickers?...Because Democrat Immigration Law is convoluted, opaque, and (surprise!!) designed to enrich Democrat Party lawyers while costing the US about $50Bn/year and importing lots of criminals-to-be, the activities of MS-13 are "hiding" in plain sight. That's what Nielsen failed to stop, although it was legal, and easily preventable. See the link.
(And yes, I repeat myself when mentioning 'Democrat Party lawyers' and 'criminals' in the same sentence. Not sorry.)