The anger you are feeling makes a lot of sense, but there are two sides to it. You are angry with her for betraying you, but you are also likely to be angry because you betrayed yourself. Being angry with her is because her behavior is a lightning rod. Whatever allowed you to stay in a painful, disrespectful relationship is likely to be fueling your anger toward her, but the real work is on figuring out why you stayed and dealing with that.
The Stanford Forgiveness Project and the book Forgive for Good by Dr. Luskin would be a very good place for you to start untangling these angry feelings. As you read this book you may want to begin individual therapy. You can find a therapist in your area by looking at the find help tab at the top of the page.