Well since everyone is openly talking about it I guess we can't put the genie back in the bottle now.
The Sylvie rumor is something I heared last
year for the first time. Couldn‘t remember where and when, but I remember the evidence was spotted in a Social Media post.
But imho the real Enchantress in the MCU should be Amora and not Sylvie Lushton
Yes, a girl on IMDB was credited as "young Sylvie", which caused this rumor last year.
Before I found out the international credits spoiled it I was theorizing this would be the case based on that IMDB credit, the fact that Tom Hiddleston apparently pitched a Loki/Enchantress story in 2013 (quote below), the fact that Sophia Di Martino is blonde, the fact that she says not to call her "Loki" and that "this isn't about you" to Loki, the fact that Loki says he wouldn't treat himself that way, and the fact that her main ability she constantly uses seems to be "enchanting" people to control them rather than Loki's usual illusions.
Tom Hiddleston said:
When I was first reading the comics, the relationship with the Enchantress was one of the really fun things I thought would be good to explore, and may have even pitched it to Kevin Feige at some point. Because she is as sneaky and as untrustworthy as he was.
They basically had a really fantastic and twisted relationship until they both say, “You know what? I don’t trust you as far as I can throw you. It’s over.” Because they keep betraying each other, in a way. So it could be good.
That said, even if she is Sylvie Lushton that doesn't mean Di Martino won't be playing some version of Amora or Loki in this show. The MCU takes inspiration from the comics but doesn't always follow it to the letter. I could easily see her either be some exiled version or reincarnation of Amora. When Thor was exiled he became "Donald Blake", and kid Loki at one point was a human kid named "Luke". Making "Sylvie" something similar but for Amora could set up the possibility of how Loki can by the end reincarnate into "Luke" (Kid Loki).
Alternatively, Sif also had a human body (similar to "D. Blake" or "Luke") after Ragnarok, which Loki took over to become Lady Loki. It's entirely possible that in the MCU Loki will get this Enchantress' body instead.
But on the other hand maybe she is just Sylvie. After all Sylvie was at least given powers and probably even entirely created by Loki in the comics. If she was somehow created by/from Loki that could help explain how she could trick the TVA into thinking she's a Loki variant plus create an interesting dynamic with regards to what she thinks of Loki. Or perhaps the fact that she's made of Loki actually makes her a version of Loki, but she has since formed her own identity separate from him and thus doesn't want to be called his name?
There's luckily still a lot of ways this could turn out.