SH's traditionally evil, no two ways about it. If she was simply selfish and out for herself, which she mostly is, an argument could be made, but she supports destroying the grove, going so far as disapproving of betraying the drow at the last second, and only shows regret after killing a bunch of kids. That's not really being neutral in my book.
Shw is neutral. She only cares about herself. She doesn't want any trouble. But she does not wish harm to others. She doesn't approve of killing tieflings, if you kill them then at the goblin party she will feel GUILTY. There is nothing close to evil, look at Astarion and Lae, do you see how they feel guilty? I'm not.
Besides, at the Tiefling party, Shadow says she was worried about them and didn't expect it herself. It can't be that evil is worried about a bunch of weak refugees. Again, if you kill them, then her romance scene closes. Obviously, she's neutral.
