She uses some kind of mass memory spell, to make it seem like she was one of the mane 6/7 all along. She wants to be someone important like they are. She’s envious of all they have accomplished, and wants to be one of the holder of an element of harmony. So she uses a spell to insert herself into their lives and make it seem like she was always there, that there are seven elements. Twilight is able to tell something is wrong though.
 
I wanted to keep her design simple, I’m not all that happy with her hairstyle and I might change it one day. I tried as best I could to make her color go with the rest of the mane 6, we already have yellow, orange, pink, blue, purple, and white for the coat colors so I went with green, since it hasn’t been used yet. I know I probably could have used a variation of those, like how Starlight is a purple-ish pink, but I thought green fit the theme better. I just used a darker green for the mane, like how Pinkie has a light pink coat and a darker pink mane. I used the shade of green from Rainbow’s mane since I wanted one of the colors on her to be one that is also used on another of the mane 6. Since that all have a color that is on one of the others. Also green representing “green with envy”
 
All the mane 6 have sort of a three part cutie mark, be it 3 separate of the same thing or three different colors on the lightning bolt. So I just gave her three clovers.
 
I kind of based the clovers on an idea from the movie Glass, where there is a secret society with tattoos of 3 leaf clovers and their goal is to eliminate the supers or 4 leaf clovers of the world. So 3 leaf clovers are regular people, and 4 leaf are those with superpowers.  
The 4 leaf on her cutie mark represent how she wants to be someone important or someone special (a 4 leaf) like the mane 6, but they are purple and not the type of clovers that are actually considered lucky. So she’s a false protagonist.
 
I gave her eyes shaped similar to Twilight’s but with four curved lashes, I wanted to give her an eye type that none of them have. Since, none of the mane 6 have the same eye type.
 
I think she would end up being redeemed.