Brodie loves reflections. When she was a puppy, she used to think her litter sister (my aunt has her, they are very similar looking) lived in the oven. She would often go and look at her reflection, especially if she got upset about something
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She is three now and understands reflections very well. If she wants something she will often go look at my reflection in the glass of the fire, and if I wave at her she will turn and run up to me