Denim. Aries is correct, and I concur with her approach, albeit in a more selfish manner. Basically, you should refuse to allow that person to live in your head! This person who has hurt you so much should have no right to wiggle herself into your brain and, in addition to hurting you to begin with; to continue on and on to hurt you non-stop! She ensconced herself inside your head driving you nuts, while she merrily goes about her way!
So, yes, there’s the element of forgiveness, and I can’t pasken on whether there are ethical, moral, or halacha requirements to forgive her, but prior to (or in conjunction with) forgiveness, you should selfishly refuse to let her continue to hurt you.