I like the idea I've read that Sylvie became a nexus event because she was going to be good, when Loki is supposed to be bad. She was playing in her room with a Valkyrie doll when she was taken, and she yelled for people to help the other guy being restrained. As a girl, she could've had aspirations of actually becoming a Valkyrie, and that would go against the path Loki is supposed to take. Until then, being a girl may not have been enough to cause a nexus event, because she could've still gone down the villain route.
Not to mention she doesn't want to rule the TVA, she just wants to tear down what she thinks is a corrupt fascist organization; something a hero would want to do.
I can buy this, although I feel the need to point out the nitpick that if Sylvie diverged because she idolized and wanted to become a Valkyrie, an all-female warrior group, then it's not exactly an unrelated distinction! It's kind of the same twist, but more, which is why it would work.
So it's plausible! The only thing there is that it starts to raise questions about timeline mechanics (namely, that a timeline with the Sylvie swap but all other events being identical is not strong enough to be considered different from the main timeline, which I am not too sure holds up) but at this point you're getting into time travel mechanic discourse and that's just insane.
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I definitely did not forget to put the 2020 GOTD Guru winner, azuarc in my sig!