Is a goddess's evil all that there is to her? We would say "no" about almost any human, and Toril's deities are actually ascended mortals.
So, Shadowheart might not be brainwashed, but right. From her perspective, following Shar may appear right in a way we would recognize as valid could we adopt her perspective. With no need for any evil on her part.
Many are ascended mortals -- AO has reasons for wanting mortals in certain positions and he changed the tablets of fate to ensure that Deities answer to their worshipers BUT Shar and Selune aren't ascended mortals. They were born as gods. They were the first two and haven't changed that much since their initial battle:
In order of appearance:
1) Shar 2) Selune 3) Chauntea
Chauntea has changed over years from a goddess of the wild places to a goddess of gardens and cultivation but is still born as a god and thinks like like a god. Of all the gods Shar has probably changed the least over the millenniums.
Indeed. And Shar's view has always been that she was the first and she will be the last. This is why even the evil gods (grudgingly) cooperate with the good gods to thwart Shar's constant stream of schemes and plots and intrigues, because by Shar's own admission her end-goal being realized will mean the end of even all the gods which of course even the evil gods are not going to support or want.
And a reminder again for people that Shar's initiation of her faithful is for them to torture and murder an innocent, preferably a close family member, to signify their break from everything except for Shar. Shar's faithful are taught that they are nothing and their lives are insignificant and irrelevant, and their very existence is only for the purpose of Shar being able to use them to further her plans. This is why throughout the Realms Shar's church is considered more a cult than a church.
