Wow, that woman is strong! Looks like a pro bodybuilder and not a cyclist.
When you say she broke cheap bikes you didn't say how cheap those bikes were if they were Walmart bikes I could understand breaking those, but if they were bikes purchased in bike shops well then how much did those cost?
If you want to keep the price relatively low then I would probably look at the Giant Stance 29 2 bike and see how she likes it. This bike is about as cheap as I would go for a fully suspended mountain bike, but it's very well equipped for the price that runs around $1,600 starting up to $1,800 for the Stance 29 1 model which includes a better fork, better shifters, better derailleurs, and better crank than the 2, plus the 29 1 comes with a dropper post, so it's worth paying a bit more and getting the 29 1 model, but you have to decide the cost value if you can afford to go to the 1 over the 2.
The only option I would consider if she's a real serious mtb'r is to get a dropper post for it.
There are hundreds of bikes out there, I just mentioned one, I think all around for the price it's a great value, but other people will mention other bikes so you need to entertain those as well, I'm just not going to spend time typing in 10 different bikes or more without knowing more details on what you want to spend.