what paperwork does my niece need to fly here alone?

Last week, my sister called me from overseas and said my 13-year-old niece wants to visit us in the US this summer. She’s super excited, and honestly, so am I—we haven’t seen each other in years. She already has her visitor visa, so we thought we were all set. But when I called the airline to double-check, the agent told me she’ll need a notarized letter from her parents explaining who she’s traveling to and why. I thought, okay, that sounds simple enough, but then I started looking for an official form from US Customs and Border Protection and came up empty-handed. Now I’m confused—every airline seems to have their own rules, and there’s no clear government form for this. I don’t want to mess this up and have her stuck at the airport, or worse, turned away at the border. Has anyone else gone through this? Did you have to jump through a bunch of hoops, or was it more straightforward than it sounds? It feels like there’s always one more thing to worry about when you’re trying to do something nice for your family. #familytravel #unaccompaniedminor #travelquestions #Travel