I think the main problem with issues like this that happened to your partner is people fear making waves so much that they don't even consider going to a lawyer

I think the main problem with issues like this that happened to your partner is people fear making waves so much that they don't even consider going to a lawyer to enforce the implied contract that she had as a grad student with both the university and the original thesis professor. Legal action is used even by unions to enforce their rights and contracts. If you don't have a union, legal action is the only strength a cog in the machine has. Use it, or get run over. I'm not just writing out of my butt, I've successfully done this once. It is risky, but is it realistically any worse than what happened in this situation? It's not as if there's only one university awarding PhDs. And if you're swapping professors left and right, it's not as if staying at the university is really benefiting your original research goals.