At some point during "Whisper of the Heart", Shizuku falls asleep at her desk while working on her story. She has a fantastic dream involving Baron and, when she wakes up, her room is larger. While her bed was right next to the desk before, there's now space for a whole window between them.
I believe this represents her personal space becoming larger with her sister moving out, but I'm not sure if there is something else I missed.