Especially considering she was making $42k annually as a teacher (according to another comment, I didn't actually read the article). So she was able to live on roughly that amount already.
Realistically, she could continue to create OnlyFans content for some time and make and invest more than the initial $1m.
I have carpal tunnel in my right wrist at the age of 29. It seemed like it started fairly quickly a few years ago. One week I started noticing my wrist was really stiff and would get pretty uncomfortable if I left it in the wrong position for too long. Looking back, there may have been a few warning signs that I needed to take more care of my hands and wrists, but I didn't really think about them when they happened. For example, I had noticed a couple times when a certain movement (specifically, holding modifier keys) would be a little painful for a day or two then it would go away.
As far as what to do to prevent it, most of the other posts have good advice, make sure to take breaks consistently and stretching is important. I also ice my wrist a few times throughout the day now, and that definitely helps.
I don't think you need to actively worry about it, but trying to change some of your habits now before anything starts to hurt is probably the best way to avoid having any trouble.
Who says he killed them first?