Xander listened to her story carefully as she told him what had happened to Riley and his counterpart from her world. After she finished he took a moment to let it all sink in, what she had been through, and finding the right words to say.
He reached across the table and took her hand.
"Speaking on behalf of your Xander, and any Xanders out there...I forgive you. The person who killed that Xander, it wasn't you. You were taken over and had no more control over what you could do than a person hydroplaning on the road. It was not and let me repeat that, NOT your fault. I know you might feel like it is, but its not. You're a good person. Sure, you might have a little devil in you," he added with a grin. "But I forgive you for what happened. The hardest part is going to be forgiving yourself. Just take the time you need, you're going to have to live with what you did, you'll keep the memory with you. But you have to forgive yourself because you had no control over what happened."
It was words she needed to hear, but he didn't forgive her to make her feel better. Sure he hated Angel/Angelus and never distinguished the difference between the two. Same with Spike, but he had grown a lot since then. This Xander and he hoped the other Xander would forgive her given the situation.