Except she's the only one that knows that (outside of devs).
At the end of the day, she has the unfair advantage of knowing who's an NPC and who's the Player. Had the Players known she's a Player herself, their strategy would probably be completely different. And you can't blame the Players for not knowing because there is zero signs of her being a Player other than the "Players can pick sides" thing (which doesn't even work in-context).
Realistically, the game should function via MMO rules where characters have their names floating over their heads, where how it's written makes it very obvious who are Players and who are NPCs/mobs.
I might have missed it - what special feature allows her to know who's a player versus an NPC?
Because so far it seems the only reason they're all convinced she's a raid boss is because she's "not on the side of humans", which--you'll have to explain how "players can pick both sides"
doesn't work in-context.
Rare says it herself - she took debuffs at the very start to acquire a bit of extra initial XP, and that snowballed into where she's landed as an incredibly powerful entity with lots of minions at her disposal. Nothing that she's done was some cheat, but pure dumb luck and a willingness to go laterally to what might be considered "conventional" in gaming, by virtue of just how open-ended this entire world and setup is.
The only gripe that I can think to have, is that she's being shown as the
only player who chose the "monsters" side, because even if the majority of the userbase is caught up in the "I'm a good guy!" mindset there should be at least a few others running around who would be working alongside her in such a huge event, even in their little corner of the world map.
As far as the "MMO rules", that presupposes that it's an issue that one can't tell who's an NPC versus a PC. Again, I'm not sure why it's relevant, because it sounds like you're basing that on the fact that she's incredibly powerful in her current iteration which--again--she didn't cheat or P2W or anything like that, or do anything that exploited the game in a fashion no other player could had they thought of it.