Board Thread:Questions and Answers/@comment-25322628-20190608065429/@comment-29390967-20190608152705

I don't think she lost faith in Eren. I think it's her simply realizing that she needs to move on on her own without being always by Eren's side needlessly and developing as a character. She probably realised what Eren wanted to say after he said he'd always "hated" her. So in my view that's the reason by leaving the scarf behind which is the precious symbol of her love for Eren.