She may look different but this is indeed Twilight Sparkle. The bracelet and necklace allow her to stay in disguise. Reason as to why? I had an idea for Twilight to be (wrongfully) banished to not a world a criminal so with help from that world’s Trixie. She finds a way to disguise herself and officially become Moonrise Luminescence a castle worker.
Edit: The bracelet makes her a unicorn and the necklace makes her an alicorn
(the closest comparison I can make is the dark mirror universe from the comics but because I haven’t read them enough to recreate it I’m making my own universe based on but likely far from it)