If the events with Nightmare Moon took place in Canterlot instead while Twilight was at Moondancer's party, who do you think would get which Element?

Hmm good question. I'm only sure about Twilight Sparkle would be the element of magic and Colgate/Munutte would be the element of laughter.
I'm not sure but I dare to say Moon Dancer might be the element of loyality. I think that was one of the reason why she took it so personally when Twilight left so suddenly and not just she didn't come to her party but she never sent any mail to her until the events of the Amended Fences.

I'm not sure about the rest. We don't know mutch from them not even from Lyra.

PS: Right now I thinking about Lyra might be the element of kindness or generousity..