I suppose that we all build walls; sometimes to protect us from harm, or to shield us from repeating a pain from the past. That self-imposed barrier will often keep people away that might enrich our lives. Also, the barriers that we build for ourselves are imposed on others and hurt them too. We see this in Pages in the Wind, when Emily realizes that she failed to reach a breakthrough in communication with her mother.
Pulling into the garage, the reality of the depressing morning was starting to get to me. I needed space from her, and the sad revelation that there wasn't going to be a breakthrough in our relationship. It was heartbreaking to know that someone that I desperately needed - didn't need me. The barrier that I hoped would tumble when we talked about Penelope - was still standing tall. Something told me that I would never be able to reach the top, and if I did - she would only add more bricks to keep me away.
The wall around Emily's mother is exactly that - a wall of despair - and one that she has transferred to her daughter. The thing with walls is that if they can keep away the bad, they can also keep away the good. This wall plays an important role in Emily's development, and the events that follow.