And i have no idea how would i pick Aligment for her ...
Seems like some type of neutral to me... Lawful, maybe? Because the character has a set of rules about who she likes/dislikes, so there is some personal agenda going on here, pretty typical for lawful neutral type.
As far as i know, as long as *you* made your decisions based on own rules ... its Neutral aligment.
If you want Lawfull its set of rules, that apply on you, but were not created by you ... you were thought them.
Basicaly i feel like i should say that she is True Neutral ...
But she isnt, since she is willing to sacrifice herself for others (as long as they are Tieflings, so she is also not exactly Good either) ...

Personaly i simply believe that characters like Zyraela are main reason why WotC stops using aligment ... its usefull guide, but its also quite limiting if you want to create something complex.