When any person treats you ill or speaks ill of you, remember that he does this because he thinks that it is his duty. It is not possible then for him to follow that which seems right to you, but that which seems right to himself. Accordingly if he is wrong in his opinion, he is the person who is hurt, for he is the person who has been deceived; for if a person shall suppose the true proposition to be false, it is not the proposition which is hindered but the person who has been deceived about it. If you proceed then from these opinions, you will be mild in temper to him who reviles you: for say on each occasion, "It seemed so to him."
It seemed so to him. It seemed so to her. That's a way of not making it "all about me" isn't it? Part of responding skillfully to mistreatment is to find a way to break out of our narcissism; being able to see things from the other person's point of view (even if we're sure that point of view is wrong) will certainly help.
I like to pair the above passage with a short quote of Marcus Aurelius - who was greatly influenced by Epictetus:
The best way of avenging yourself is not to become like the wrong-doer.
Can you imagine what a different world we would have if that bit of advice were widely followed? We can train ourselves to follow it, no matter how counter-cultural that commitment may be. The very real danger is always that we will become what we despise. Letting go of anger and hatred will prevent that great ironic reversal from taking place.