I like the idea of SH being a selunite. My own theory is that she's not just a Selunite but a corrupted avatar of Selune herself. SH doesn't know much about her background but the other companions were very high level before capture - Gale would have been lvl 20 and a chosen so an avatar would be at that same level.
The other outside possibility is that she's a silverfire wielder.
Don't get me wrong I have plenty of critiques of BG3 but this isn't one of them - SH as Patty Hearst sounds fun. I just like redemption stories.
Here I may be spoiled by playing Bg1/2 with Viconia on my team, and she was not shy about voicing her preferences, with cries of "Nightsinger, grant me strength!" or "For Shar!" ringing across Fearun.
Admittedly, I have a whole headcannon about Viconia but the romanced Viconia doesn't behave like a good Sharran. Can't remember what triggers it but there is line with a good charname that suggest Shar isn't entirely happy her. The line goes something like "if I did that Shar would be even more upset with me than she is right now . . . "
SH is acting more like a Sharran cleric would. If anything she reveals too much too early.
