Why my best friend doing this every time?

Hello everyone.
Whenever me, my boyfriend, and my best girlfriend went for a walk, I noticed my best friend tried to walk between us. At first, of course, this little detail didn't catch my attention, but when this situation became constant, I started to notice it. Even when we sit at a dinner table, the person sitting across from my lover is not me, but her. I really don't think she did it on purpose, but what is her subconscious? Is this normal or is it weird?
Why my best friend doing this every time?
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