Years before your spouse enrolled in that Amazon course, people were spending tens of thousands of dollars on Trump University. Many years before that I had a friend that got sucked into the Equinox International MLM scam. Point being those types of promises of easy money after paying for a course, or outright scams, are not something new or unique.
The vast majority of people who fall for things like MLMs will continue to pursue similar scams and never graduate to "real entrepreneurship" even when there's obvious and not terribly difficult paths (most anyone can become a realtor and at least not lose terrible amounts of money, even if they never get to "full-time job" levels).
She also has a few art shows she applies to and goes presents at those. I think this is where most of her recurring customers come from honestly, and not Instagram. Though she has had a few commissions from Instagram.
A side note on those looking to buy art, you might refrain from asking for a custom piece. If you see something you like, there's a good chance you don't know why you like it even if you think you do. So when you give the artist a picture you want them to translate into something like oil, it'll probably disappoint. The frustrations I've seen my wife go through trying to get a commission right is tiring.
The dog walking business example was also appropriate in my mind. My spouse fortunately broke even, minus time, on her attempt with drop shipping garbage nobody really needs. Now she makes decent money with her oil paintings. Not "passive income" but real money and profit. Not enough to retire (that's what I am for!) but actual money nonetheless.