Now, Celestia and Luna were the holders of the elements right? But i don't think both have all of them, so here is what I think belonged to who. But first lets ignore the part that Magic and Loyalty are elements:
- Kindness and Generousity belongs to Celestia, because Luna can get angry and greedy faster than Celestia, and Celestia shows kindness and Generousity ALL THE TIME! I mean, Pinkie ate a whole cake and Celestia didn't mind, a normal princess will send Pinkie to dungeon just for that!
- Honesty and Laughter belongs to Luna, did u ever see Celestia participate in Nightmare Night? She wanted to have fun and make others not scared of her. And she was quite honest even when she was Nightmare Moon.
- now Magic and Loyalty belongs to both of them, because of both of them being really loyal to their subjects. Except when Luna turned to Nightmare Moon, but I don't think that she turned on her own, the comics proves it. And come on! Two Alicorn princess who raise the Moon and the Sun on a regular basis do deserve the element of Magic!