Um...it's a bit too late for anybody to not be getting in the middle of this. Including, now it seems, Dr. Sullivan. We already knew that she has some connection to "A", and now by the end of last episode our suspicions are confirmed - "A" is a patient of hers.
Check out the promo for season 2, episode 11 of Pretty Little Liars, "I Must Confess":
Source: ABC Family