Personally, I think that A is a girl. The texts sound like a girl's writing, not a guy's. But I don't know. I guess that girly text message "tone" could be faked.
And I mean, "A" doesn't have to be the same person that the killer is. Like, the killer and A could be working together if you get what I mean.
Yeah I like her better with Mr. Fitz. That's actually a good idea, to keep up the whole Noel thing as an act to eliminate suspicion. Because you know, Mr. Fitz would be fired in an instant if he and Aria were found out.