Or by her participating that she is knowingly involving herself in a scam. Which, yeah, it's just books - but it's pretty obviously a pyramid.
No shame if you don't see how it's a scam, the cozy blanket and glass of wine are meant to throw you, and they chose 36 because it's a confusing enough number where you don't think too much about how it grows.
She gives one book to her upline. She then sends out post to 36 more people to give her 36 books. Each one of them then needs to find 36 people each, which is now 1296 people in that level if they each want 36 books. Thus the exponential pyramid. Of course there is zero way each of them will find that many people, let alone the levels below that. It's a scam that benefits those higher up, and the ones lower will likely not receive anything.
Of course she sees nothing wrong with that. She said "Sometimes I get books, sometimes I don't, that's just part of the game". Which... it's not a game when it's real money being passed around.
On top of that, whenever we see a pyramid scheme we should be stamping it out - hard. Folks, please spot the signs and point them out. Don't be afraid to comment on posts calling them out as scams.
Edit: To be clear the idea of a growing book exchange isn't a bad one, as explained in the comments though the way to make it not a scam is to make it 1:1. You either send a book and receive a book, or if they like the 36 number, you change it to "I'll send a book to whoever sends me a book!". Then it's a true book exchange.
Who is higher up? Who benefits from you buying 1 book to send to a random person and how? Maybe I don't even buy a new one; I just send out an old one I already had. Or is there more to it than the image shows and you're supposed to be buying a book from a specific supplier?
This seems more like a "pay it forward" gift exchange than a scam.
Pay it forward would be fine if it was 1-1, you gift a book to one person and you get one in return. The scam is that you get people in thinking if they gift one they'll get more than one back. Of course they probably won't, it'll quickly collapse.
Pay it forward things aren't 1-1 either. You're not guaranteed to even get anything back yourself most of the time. It's just to feel good about yourself. Like paying for the people behind you at a drive-thru.
But I can see how this gives the impression that you will.
but pay it forward can work in theory
this can't even work in theory because books entering the system 1 at a time and leaving the system 36 at a time requires 35 books to be conjured out of thin air
I think the idea here is that 37 people send 1 book each and you could be the recipient of the other 36 you didn't send since you're all on the same list and everyone is choosing a recipient at random to send their book to.
how could you know the total participant count is 37 ahead of time if you're currently looking for sign ups
also, a book exchange of 37 people doesn't strike me as particularly "huge"