8. You Never Have To Knock On Their Door
You even have your own key. Your best friend will give you their heart and their fridge, which are the two most important things anyone can give someone. You treat their house as your house and if you're lucky enough to live together, then their room is your room. She will never get mad when she gets home and finds you napping in her bedroom because chances are, she'll just get in next to you and wake you up gently to hear about your day.