Based on what she says I don't think there's any misinformation going on about Shar from Shadowheart.
Shadowheart isn't misinformative but biased, and she should be kept as such because she is a Sharite and that perspective is part of her character (and likely, her character ark). The "standard" (I can't think of a better way to put it in English right now) view on her is that I feel needs to be conveyed would be Shar as an Adversary deity. Shadowheart's perspective should be something that contrast with and add nuance to this "standard" view most people would have.
