7th Element, or just Shared Element

There's been a lot of talk going around about Sunset Shimmer being a 7th Element of Harmony, yet we all know that since the beginning of the MLP:FiM franchise there has only been six Elements of Harmony, I believe that there is actually more to it than just that, I think that the Elements of Harmony actually works similar to how Mjolnir the Hammer of Thor the God of Thunder(especially the Marvel Comics incarnation) works, meaning that only those who prove that they are worthy of wielding the power of the Thunder God may wield the hammer, by proving that they have special attributes that make them worthy enough to use Mjolnir and gain the power of Thor, there was even a time when Thor Odinson lost what made him worthy of wielding Mjolnir, and Jane Foster became the new Thor because she was actually worthy of Mjolnir's power.

For example, we all know that both Celestia & Luna used the power of all six Elements of Harmony to accomplish many great feats a long time ago, Celestia was worthy enough to wield the power of 3 of the Elements, and Luna was worthy enough to wield the power of the other 3 Elements, but after Luna became Nightmare Moon, she lost what made her worthy of wielding the Elements, and after Celestia used what little power she could muster from all 6 Elements(but not the full power of the Elements) to banish her own sister to the Moon for 1000 years, she too lost what made her worthy of wielding the Elements power, so Celestia began a search for someone else who would be worthy of the power of the Elements of Harmony, more specifically the Element of Magic, the other 5 Elements would have been much easier, but the Element of Magic would have been a real challenge to find one who is truly worthy of such a rare & special power.

It's most likely that Celestia took in Twilight as her prized pupil, because Celestia could sense that Twilight had the right qualifications, but Twilight could truly use the Element of Magic unless she learned of the power of friendship, so Twilight was sent to make some friends in Ponyville, and the Elements of Harmony found six new worthy wielders, and I'm sure that back in the 2-part Season 2 Premiere(that introduced Discord to the franchise), they could have been able to use the power of the Elements with Spike as Loyalty(due to how unbelievably Loyal Spike is to his Friends), if only Spike's heart was in it, and if Discord hadn't suppressed what made the Mane 6 worthy of wielding the Elements in the 1st place.

Plus (*Spoiler Alert*) in the 4-issue story arc of the Official MLP:FiM Comic Books by the IDW Comics Company, entitled "Reflections", they story where the Mane 6 + Spike traveled to a Reversed Alliance Universe(Where the Heroes are the Bad Guys, and the Villains are the Good Guys), and took the Elements of Harmony with them, and by the final issue of the story arc, the Good King Sombra wield all 6 of the Elements, to drain the Evil out of the Evil Celestia & Evil Luna, and transferred it all into himself, thus turning the sisters from Evil to Good, and turning himself from Good to Evil, it's most likely that because of the fact that he was a Good King, he had enough special qualifications to be worthy of wielding the Elements Powers(even though it may not have been the Elements' full power), and by turning himself Evil, he ultimately lost what made him worthy of wielding the Elements' Power.

Of course just because Thor Odinson has remained worthy of wielding Mjolnir, doesn't mean that he could be the only one at a time, this was proven by the Marvel character Beta Ray Bill, who was shown to have the worthiness required to wield Mjolnir, but later he was given a Hammer of his very own called Storm-Breaker, which was a different shape & type of Hammer, but it still possessed the exact same power as Mjolnir, and only one who is worthy may wield it.

And in the Equestria Girls side of the My Little Pony franchise, we got introduced to Sunset Shimmer, who was revealed to have been Celestia's prized student Before Twilight Sparkle, and if she was Celestia's prized student, then Celestia must have seen something in Sunset that made her have the potential to wield the Element of Magic, but because Sunset was a cruel & hateful character back then, she wasn't worthy of the power of the Element of Magic, so when she tried to use the Element, due to her unworthiness, she ended up becoming that Succubus-like Demon.

But with the help of Pony Princess Twilight & the other Human Mane 5, Sunset eventually found redemption, and by the Friendship Games movie, Sunset had learned of the exact same thing about the Power of Friendship that Pony Twilight had learned back in Season 1, and had regained what made her worthy of wielding the power of the Element of Magic, which would most likely explain why Sunset was able to take the powers of Applejack's Honesty, Fluttershy's Kindness, Pinkie Pie's Laughter, Rarity's Generosity, and Rainbow Dash's Loyalty, to take on that "Day-Break Shimmer" form thing, which sounds more like something that we'd see Twilight Sparkle do, which could most likely mean that Twilight Sparkle & Sunset Shimmer are both worthy of wielding the power of the Element of Magic.

And in the Legend of Everfree movie, when the Human Mane 6 + Sunset all received those Rainbow Geodes(which I don't actually consider to be the Human World's equivalent of the Elements of Harmony from Equestria, but merely another plot driven power-up gimmick, like the 6 Rainbow Keys from Season 4, seeing as how there have always been only 6 Elements and those who are worthy of wielding them), it's most likely that like Mjolnir & Storm-Breaker both representing the Power of the Asgardian God of Thunder, Sci-Twi's & Sunset's Rainbow Geodes would both represent the Power of the Element of Magic.

So in Conclusion, I believe that Sunset Shimmer does not wield a 7th Element of Harmony, but merely she is a 2nd being who is worthy of wielding the Element of Magic, thus giving us 2 active Element of Magic Wielders in the Mane 6(Pony or Human), so please feel free to tell me your thoughts.