Do you remember the scene in S3Ep2 "sick" where carol is disecting a female walker? Someone was watching her. It's kinda important and significant to be forgotten. That scene might have meaning. It's almost season 3's finale and that part is never explored. For me, that should be explained. Why would they add that scene if that doesn't mean anything at all?
This scene also has a counterpart in the comic series. Two woodbury soldiers were spying while andrea and some other group members were practice killing some walkers around the prison's perimeter. Those woodbury soldiers were the one who told the Governor where the prison lies.
I don't think that a woodbury soldier was watching Carol. If it is, they would have told the Governor about it sooner. Who do you think is/are watching Carol? This should be explained briefly.