Bear thinks yours definitely sounds more like a real teenager than mine does. Thanks for the helpful feedback!
I think I was trying to fit way too much info into one dialogue snippet, as well as still not hitting the target on actual teen rhythm and speech shortcuts, which I think you nailed on the head.
I'm in the same boat concerning "diss" and "cool". I THINK "cool" is currently back in, with about the same use as back in 1960's talk, but am wondering if it's STILL in, or if it's "out" again and no longer safe to use? (When I say "cool" to random teenagers to test it out, they at least don't
their eyes at me.)
"Diss" apparently came in about 5 years ago or so, and I THINK it's still used quite a bit. So I tried to use it, but had to look it up on the Web to figure out the exact way to fit it into a sentence, and I could be off on it. I envy those with teenagers in their house, who have real-life examples walking around them all the time. Because I really would like to learn to write for teenagers.
Here's one web definition I found, googling . . . "diss -- treat, mention, or speak to rudely; "He insulted her with his rude remarks"; "the student who had betrayed his classmate was dissed by everyone" "
I especially like your use of "gonna", as that sounds much more natural.