Ann,
Welcome to PA! Glad to have you here!
I'm reading your app and I have a few things. First, our setting is the future, Its 2026. Voldemort, Mrs. Norris, etc., are dead. So that will cause you to need a few edits. If you were to simply say she is dedicated to becoming a Death Eater, that would resolve the serving Voldemort issue. And if she siply didn't like one of the cats of one of the members of Slytherin house, that would resolve that as well.
Where does the nickname Knightwalker come from? You don't explain that. I also need you to fill in, if you're going to have a photo of someone that your character looks like, who that person is, and it needs to be someone that is not already being used on our face claim list. It needs to be a photo, not anime, please. The same for your siggy and your avatar, please.
If she is going to be a Slytherin, what are the qualities of her personality that make her a Slytherin? I generally look for someone who is devoted to either family or to time honored traditions of wizardry and the preservation of wizarding society. At this point, the fact that she does have dark tendencies does help her a great deal, and that's a good thing, but if you have any more to add there, it would help.
Her blood type would be halfblood b/c we don't allow purebloods now except those who are canon characters. I presume the Queen reference in her race has to do with personality, rather than any assumption of royalty?
If we admins can be of any help in making this whole polishing process easier, do just speak up. We're always happy to help!
K.