I love the fact that she is evil but not absolute evil and she has a deep personal drama in her backstory. Most likely, she can be really good with us if she will trust and respect us over time, and we will show that we will not betray her for profit as is customary in drow Lolth society
This as far from truth as it can be. She is psychotic sociopath that fits a serial killer profile. She kills for pleasure and without any reason. If you don't think this is absolute evil then I don't know what to say. There is no drama in her backstory, she's a typical drow, who is paranoid to be backstabbed.
Killing for fun in a computer RPG is so-so sin, considering that most of the game we fight someone, and even a good hero can enjoy the sophisticated killing of some asshole. Think of Dragon Age Origin and Arl Rendon Howe, even the kindest heroes would like to torture him slowly and enjoy.
It's just that in this case we kill tieflings and not bandits in the chapel. And we kill tieflings and merchants not in a boring way just for the sake of loot, but on a quest in a more interesting way.
It is normal for drow and people like Astarion to take pleasure in violence. What she did to Sazza is pretty good, goblins are dumb evil minions and it was a fun scene.
The subject of determining whether she is absolute evil or not is her relationship with her compeer who are trying to be friends with her.
My attention was drawn more to the scene with her fears, as well as the fact that she say words of regret, apologizes, and offers help after checking her beliefs. In my understanding, evil from absolute evil is distinguished by the fact that absolute evil would simply attack us of its own free will and there would be no unnecessary words and scenes. Like Kagha, by the way, but I hope it's just a bad writing job at EA.
She also must have had reasons to leave Lolth for the Absolute, when she talked about the drider it seemed to me that she disapproves of Lolth and is glad that nothing else is with her. She might have failed Lolth's test, or something like that. There is a reason we need to find out. Lolth is also absolute evil. Compared to which the actions of Minthara are not so evil, it would be ideal for her to act in her own interests that would coincide with the interests of the protagonist in the first place, and not in the interests of the cult of the Absolute. But still stick to the same style