Did they say you have to be “purest” of heart? Or pure of heart? In comparison to many on the show, Snow is still pure of heart. Even her murder was for the greater good. And she has and continued to try to atone for murdering Cora. Most importantly, I think, she continues to try to atone for her actions, even though she knows she never will be able to completely. I think that’s what makes a person pure – not prior acts, everyone has those, but the desire and attempt to truly be and do good in the now and future.