Things got seriously ugly when her products started to get to the top of the search results. This took time and a ton of money and effort. That's when the attacks started.
Two forms of attacks prevailed: Fake reviews and click fraud.
Competitors would post completely fake reviews about her products. They would claim things such as having had to go to the hospital or having diarrhea for three days straight. All false, unverified. The other way you could tell the reviews were fake was when the review posted before the product shipped out of the Amazon warehouse. I could not believe Amazon didn't have just a little bit of common-sense code to automatically reject such obviously false reviews.
Sellers can advertise on Amazon. We did. Once her products started to show up at the top of search results her ad budget would be consumed in its entirety by 4 or 5 AM every day. You could look at the analytics and see, plain as day, that all the clicks happened during the span of an hour between 3 and 4 AM eastern US time. Thousands of clicks every day. This meant that our ads did not show by the time people got up.
Oh, yes, the other method competitors used was to contact Amazon and make false claims about her products. They'd claim we were not disclosing true ingredients; fake copyright violations, etc.
It was all-out war against her in the worst possible way. At the time I remember thinking that this experience had to be an approximation of what it would be like to deal with the mafia. I had never seen such dishonest, criminal behavior in my life.
I captured analytics and put together analysis to show Amazon what was going on. Her business was being destroyed at a rapid rate. It was relentless. Amazon could not care less. It was impossible to deal with them. I persisted. It took them about six months to finally admit our data showed a coordinated effort on the part of competitors to destroy her business. They also claimed they identified who did it but refused to give us the information. They issued a refund that amounted to tens of thousands of dollars in wasted advertising. Never mind the hundreds of thousands of dollars in lost sales, nobody paid for that.
In the end we decided we had zero interest in dealing with the mafia and quit, which, ironically, was probably exactly what these criminals wanted. We make more than enough money with our day jobs and tech business, no need to complicate our lives in that kind of an environment.
My experience with Amazon, in this regard, was an eye opener. Today I do not buy anything on Amazon that isn't marked as "Sold and Shipped by Amazon". I want nothing whatsoever to do with their third party sellers. That entire ecosystem is permeated with people you just can't trust, even if all you are buying from them is a spoon.
I still have friends I met along the way who sell on Amazon. The stories, years later, remain the same: Amazon does not seem to care about criminal behavior on their platform so long as they are making money.