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Earlier than that, Hotaru Tomoe (known to the masses as Sailor Saturn) existed. Some sources say that the term 'moe' is actually derived from her last name, Tomoe. Evangelion was 1995-96, whereas the S season of Sailor Moon in which Hotaru appeared aired in 1994-95 and the manga where she appeared came out in 94 as well.
I'm not saying Rei copied Hotaru by any means, just pointing out that Rei didn't create the stereotype. She no doubt popularized it however and shaped the stereotype into what it is now.