I think you may be overreading the text. The writer could also be just saying they feel really stuck. It's a common problem in small companies, especially in cases where it's hard to hire replacements.
They would have to hire two whole employees to do her job, and pay them market wages! Jean works for less because she likes what we tell her to do, and she doesn’t need the money. Instead of maybe paying a little more to ensure the business would continue running in the case that Jean leaves or even just falls sick for an extended period, they would rather look for ways to lock her in (it doesn’t really seem like pay raises are on the table though). This just reads like textbook exploitation to me.
It's hard for me to believe anyone can assess a human being from one ambiguous sentence. This is not Twitter.
Well anyway, during the summer there was this coding contest and I won 2nd place. The contest was a recruiting stunt, no surprise, and I was offered a job. I said yes for Jan. They really wanted me ASAP and I explained my situation. They offered to pay that out and a signing bonus, so I said yes negotiating to start in a month to hand over ongoing work. Funny thing is, if I'd given my word I would have stayed to the end of term. Putting the penalty clause in the contract actually made it so much easier to leave because the conditions were so cut-and-dry for both parties. So my take is that you shouldn't run your business on money and fear, but rather get to know who you're dealing with.
Now that I'm thinking of this, I was in another similar situation, where I had my full-time programming job but was bored and got a summer job at Sporting Life (upmarket sportswear + equipment chain). I onboarded for a week with a bunch of highschoolers off for the summer, aced the textiles knowledge. At one point they pointed out that I was far overqualified for the position, and I said that I was bored and the employee discounts are pretty good. Anyhow I ended up staying there all summer, fall, and most of the way through the winter, outlasting multiple waves of staff turnover. I gave it up because it was stressful to get there on time, finding parking, and the parking tickets were racking up. The best part of the job was when ladies trying on clothes would ask how things looked and I'd give it to them straight. I don't recall anyone being offended and many thanked me for my honesty and bought stuff. I wasn't on commission but would have done the same anyway. [I'm a bit socially autistic-like, I once declared that a friend "wasn't at all photogenic" and there was dead silence. Part of the problem might have been that I looked at a lot of photos of them before I said it. I still didn't think there was anything wrong with saying that. It seemed the same to me as saying you're not tall.]
I guess there's a chance where it was just poorly-articulated "one of my employees has a stronger negotiating position than I'm conformable with." But had that been the case, the question-asker would already know the answer. The answer provided was to actually negotiate rather than expect to get their way, and work to improve the company's resilience in the areas where they're dependent on a single supplier.