Yes, A is a team, but there is always a leader, or someone who started it. I think if A were a boy, it would be very interesting because most of us have always believed it to be a girl. I think Uber A is Black Widow though, which is obviously a girl.
I've had that very ugly thought myself. Here's the reasons why: Marlene said in an interview that she really likes this actress. She was in attendance at someone's funeral (wilden's, I think) long before they ever brought her in as a speaking character. She was in Radley. Mona does what she tells her to do. When Mona goes to RADLEY and she is talking to herself one voice sounds like Mona then the voice sounds like Lesli. She wears those ugly fake glasses just like the masks people. We see her throwing a fit telling Mona she screws everything up which displayed Charles' mental profile from Radley. If we go back to season one we see a girl at Alison's funeral that resembles her a lot paying attention to the liars. This isn't who we see as Leali now but in the same episode Toby, JESSICA, and Jason are all portrayed by other actors as well. I'm posting a pic of this (back left corner, very visible if you watch the episode). By the way, I Hate this theory, but I can see evidence. I would not be happy if this is who AD is because they do not consistently show her. I want it to be someone that has had a pretty major presence on the show.