There is a common prayer called the serenity prayer that includes a line about accepting the things you cannot change. The idea being it's not worth stressing out over aspects of your life that you have no control over and to instead focus on what you can do something about.

She is playing off that by saying she's no longer going to accept those things and is now going to fight to change them. I'm not familiar with her but presumably this would be regarding fighting injustices in the world.

Here is the full prayer (or at least the version I'm most familiar with):

God grant me the serenity to accept the things I cannot change, Courage to change the things I can, and Wisdom to know the difference.