If I had a dollar for every time I've seen an older person that doesn't even know what application they're running, or can't tell the difference between the content of a website inside a browser window and an application that runs natively on their computer. I read what the GP wrote, I'm saying there's a non zero possibility she's misunderstanding something.
It seems like something you have to specifically choose, on the amazon account side.
https://www.amazon.co.uk/gp/help/customer/display.html?nodeI...
I choose to not call a GP a liar or too thick for being unable to differentiate between apps :)
I also chose their presumed first hand statement than your unrelated experience with unrelated third parties.
Your point re: having to subscribe to WhatsApp notifications, if we're staying in the realm of "what ifs" and looking for the awkward but possible ways to discredit the claims, I can believe that she was enrolled without being asked. I've seen at least one person complaining about that exact scenario.
Cheers!