Nimune says that I can find her on the outskirts of the royal city but I still haven't found her. Is she not in the game yet or am I missing something?

the same camp where you sneak into the city though I think they may be bugged.

She's present in the camp in .36 build (as the lost spirits from grey chests were tied to her) but appears to have been dummied out/removed in the .400 build, possibly due to the lost spirits now being tied to rebuilding the mansion.