Emotionally Exhausted

Part of me wants to forgive her. I really really do. I miss my friend. But I don't know how. It would be relief not to feel the hate that I feel for both of them. But I don't know how to forgive this. I don't feel like I have it in me to forgive this. It's too much to forgive. When I think about them separately, I feel like I could forgive them, but thinking about them being together behind my back brings back that hate and the frustration and the sadness that I feel for both of them. And it's not like they're from 2 separate parts of my life. She was always at my house, and he lives here too. The thought of going back to her constantly being at my house makes my stomach churn. The trust and faith in both of them has left my mind and my heart. Things would never be the same. And what's the point of trying to resume a friendship that I don't have trust and faith in anymore? I'd always hold it against her, I'd always resent her for it, and I'd always be paranoid that it would happen again. So what am I supposed to do?