[vacri]

Does she also have a problem that Amazon takes the lions share of the remaining money, instead of it going to the authors? Amazon is just another MITM - a facilitator of getting product to consumer.

Same argument with the kindle, right? "Amazon got their benefit when they sold her a device"?

Perhaps she doesn't realise that the App Store is the same kind of service that Amazon provides - after all, the Kindle is also locked down. You have to do Frowned-On things to read your other ebooks on it.

Perhaps you should inform her of this, and watch her mental model break yet again.