Dreams about loved ones who have passed, such as your Nan, can evoke strong emotions and often reflect our feelings of loss, nostalgia, or unresolved issues. In your dream, her house represents a place of memory and connection to your past. The act of locking the back door suggests a desire to protect your memories or maintain boundaries regarding those memories.

The appearance of the girls who seemed interested in entering the house might symbolize external influences or people in your life who are trying to connect with you or invade your personal space. Their actions of tidying and cleaning outside could represent a need for clarity or order in your life, perhaps hinting at aspects of yourself or your environment that require attention or care.

The woman who commented on the smell of the flowers might symbolize the presence of beauty and remembrance in your life. It could also suggest that you are beginning to notice the positive aspects of your memories, even if they are mixed with feelings of loss.

Overall, this dream may encourage you to reflect on how you honor the memory of your Nan and how you manage your current relationships. It could be a gentle reminder to create a balance between cherishing the past and engaging with the present and future. Consider what aspects of your life may need some "cleaning up" or attention, just as those girls tidied the outside spaces.