Although she is an antagonist, she has a strong moral code and believes very strongly in her chivalry, despising useless violence against the weak. She is fiercely loyal to her lord, which isn't really evil, although I estimate that her own morals may take precedence over her orders if she would ever have to choose.
Of course, being an antagonist, I wouldn't say she is loyal good, but she is not evil at heart. She may take some overly destructive methods to do her job as a loyal knight and is perhaps more zealous than need be, but she isn't bloodthirsty, and wouldn't kill without an extremely good reason for doing so. Admittedly, she has committed some seemingly awful deeds that every enemy of her source game have which would deviate from her moral code, and while I used to simply knock it off as being simply a necessity in her source material, recent horrible developments would indicate that it may simply be because it's what she has been exposed and had to suffer through herself.
It could simply be some form of subconscious revenge, which, despite being a fairly disappointing trait as I had always seen her as being a completely honest and direct type who wouldn`t ever react to situations in a passive-aggressive manner, would indicate that it isn't really voluntary malice.
With all that said, I guess the alignment that would best describe her would be lawful neutral.