Diane's primary concern appears to be coolness and not being a nerd. It's entirely possible the right pair of sunglasses is all it would take to win her approval.
I don't know how strong a griffin would have to be in order to claw up asphalt like that, both in terms of musculature and claw durability, but I'm assuming it's somewhere between "very" and "monstrously".
One reader actually commented on twitter about how patient Tara was suddenly being with everyone, and knowing this moment was coming, my response was simply a wink emoticon ;)