I'd say helping her leave and get her next job was the best thing you could have done for her.
Even if someone had solved this particular crisis, it sounds like she wasn't going to thrive in this political environment anyway. At that point, leaving is the best choice and, all too often, people don't see that.
What I did: "I told my manager," "realized it's a systemic problem," "I was a friend to someone who needed one," "I helped her leave and get her next job," and "I quit."
I made lemonade and enjoyed time in Europe. But I don't think there was a choice to fight.