@SueEllen0 I don't think it's any of your business. If she rents off-platform, that's up to Airbnb to catch. And plenty of hosts list with other platforms and through direct bookings- Airbnb doesn't own your listing. It's just not kosher to use Airbnb to suck in guests and then try to book them direct. And it's actually not at all to a host's advantage- hosts who have allowed pre-viewings say that it was a total waste of their time- the guest never booked and/or wanted to chisel them down on the rent.
Unless she's an experienced host, she could just be naive- plenty of new hosts will put their address or phone number or a photo of the front of the house with the house number clearly visible, and when other hosts on this forum take a look at the listing and tell them they shouldn't do that, that it's a security risk, they say OMG, thank you, that never occurred to me.