Emotional Breakdown

So I just need someone to vent to or something. My sister has always been a cheater and a liar. She cheated on her 1st husband, cheated on the man she cheated on with, and kept doing the same thing. Well she got married again a little over a month again. He is a great guy, yes he had a few problems, yes he had a temper sometimes, but he LOVED my sister and her sons. Well she had another affair, and he found out. He posted it to Facebook, all her conversations, everything. Then he went quiet. We found out that he had shot himself in his truck in front of their house. I'm heartbroken. We had just started to get used to each other, accept each other and care for him. He was a great guy and didn't deserve this. Now, my sister has the audacity to boast about her new boyfriend, and how's hes like us. And how her husband was terrible. It was her fault! My heart is breaking each minute I have to sit here and pretend like nothing is happening. Sit here and listen to her laugh and home, while the man who loved her lies in a body bag, while his 2 sons and her 2 sons have yet to know that their father is gone. That he's never coming home. I know I'm supposed to forgive and hate. But I hate her. I hate her so much I cant breathe.