There’s a better option for the ‘niece’ now anyway: Just go to Mexico and walk across the U.S. border. All the cool kids are doing it. They’ll give you a card with a number to call when you are settled so you can arrange for a green card and a free bus or plane ride to a city. I know of some Canadians who have talked about doing that instead of following the onerous legal process.
But yeah, there’s an old saying that you can’t con an honest man. Any offer that requires you to break the law or that offers some kind of unusually large compensation in return for some sletchy behaviour should have alarm bells ringing in your head. Avoid like the plague.