You essentially have one of two choices. Care about her emotions or don’t. If she doesn’t care about yours and is just being selfish then the choice is clear. She doesn’t care how you feel, so why should you care what she feels? Sad and angry, who really cares? Nobody ever cared when I was sad and angry, they just told me to get over it. Do the same to her.
If she made promises that she didn’t keep then she doesn’t care about your emotions. If you want to make one last-ditch effort then you can tell her that she made promises she didn’t keep and see what she says. Maybe she’ll make more promises that she won’t keep. Who knows, maybe she’ll see the error of her ways.
You choose how to react to this, not her.