Yes, you absolutely have to let it go. You made mistakes and she is gone and you need to use this lesson as something to learn from and to grow. I know it's sad and disappointing. The things we do as addicts cannot be undone and that's the hardest lesson of all. It's likely she said what she did in anger, but I think the message to you is clear. Move on and try to forgive yourself for what happened. She may or may not forgive you, and that's not up to you.