Maureen's bedroom was only shown once- briefly- in the episode Wrong is Right in season 2. In the first season, Maureen has been in her room off camera, to either be away from her father (Chat Room) or was grounded and was kept in her "cell" (Sophmore Jinx). It's unclear if she shared her bedroom with her sisters. Maureen moved out when Kathy left Elliot, moving to her maternal grandmother with her mom and siblings. However, by season 8, Maureen had moved out.