Here´s the deciding difference, Kray:

Rem is now in love with Subaru.

That single fact changes EVERYTHING. I couldn´t forgive her the murder on Subaru before, as she got to live on without any repercussions from Subaru´s side. He had all the reason to be mad, but her simply ignored that that loli girl murdered him. But that changed. This loli girl now is absolutely devoted to him. It´s not just the "i love you"-scene from episode 15. Even before, she was there for him, kept supporting him, head on lap, smiling, all that stuff. There´s nothing cheap about their relationship, she honestly loves Subaru. And that has me forgiving her. Seeing her follow through her affection towards Subaru by going full-Guts and coming to save him only cemented that feeling. She´s genuine, not some stereotypical moe-loli character type that she was before that.