How do you forgive someone who took great pleasure in your pain?

I'm trying to forgive my ex for the pain that I endured. She intentionally set out to hurt me in many ways and it almost killed me. I loved her more than my own life. I lived with constant suicide thoughts for 16 months and she egged on these thoughts and even laughed at my pain and desperation. I must forgive her in that if I don't, God won't forgive me for my sins. I also know that this pain only hurts me, but I am struggling so hard to lay it down. I truly am desparate, it has been years.