You say you lean toward clarity, but that wasn't clear at all. Like I said, you put three people in the sentence. Raven, she, and John. Now, 'Raven and John have been best friends since third grade' is perfectly fine. It was the 'since meeting' part that made the sentence not make sense. As for how you write vs how you speak, in dialogue I'm all for writing like you talk. But in the prose itself, you really should follow basic rules of grammar and punctuation, unless you have a very good and compelling reason not to that furthers your narrative artistically (Cloud Atlas, A Clockwork Orange, and Flowers for Algernon are examples of titles that purposefully did this, and to great effect).
Edited to add: I believe in writing the story you want to write, the way you want to write it, and I'm not one to enforce hard rules about how to tell a story. But it should be told in a way that the readers can understand, and that's why we have spelling, grammar, and punctuation rules and conventions; so that we can communicate our message to people in a way that they understand. That's the whole purpose of language.