What Ecc2ca said, you need to keep her in your party throughout the first 2 acts to see all the cracks in her conviction.
Apart from all the moments she gets punished by Shar for showing kindness, a quite telling dialogue happens if you save the grove and she comments how she never thought she'd find herself caring about the tieflings. On the other hand, if you massacre the tieflings, she's sorrowful about it and gets drunk to not think about it too much. The longer you travel with her the more you see that something doesn't add up when it comes to her background story, until the confrontation with Aylin confirms that suspicion. Even if you ask her if being a DJ is truly what she wants she doesn't sound like she's fully committed. If I remember correctly she says 'I THINK that's what I want'. Basicly, she makes all these pro-Shar statements, yet you can see her inner conflict, and that in the back of her mind she can sense that something is not right, but she's in denial.
If you don't spend much time with her and don't see her hesitation, there is a fitting response you can give her how you're surprised she spurned Shar. The game has multiple hidden interactions that truly let you understand characters only if invest time in getting to know them and journey together, not just keep them in your camp and chat with them there.
