Thank you for your response (and sorry for the late reaction on my part). “If I were you” is a bit of a lazy shortcut for parents. It is of course hard to squeeze your size 10 feet into a small child’s shoes, and your credibility is weak.
I guess here too the ‘what’ instead of the ‘why’ perspective may help. As you say, your best friend not talking to you is the most important thing in the world. As a parent (or general grown-up), the knee-jerk reaction is to look at it with 25+ years’ distance and dismissing the taciturn friend as an irrelevancy. A better approach would be to imagine what, for you, would be the most important thing in the world — that is more likely to give you an understanding and appreciation of what the 8-year-old is feeling. And then you can (if you still feel like it) begin to lecture them about what you would do if you were them… :-)