OMF: The difference between Ritsuko and Misato here is that Misato has already begun to think of Shinji as a person and not just a pilot.
Reichu: In the original Japanese, she says kokoro. This, along with ki, are abstract, spiritual concepts referenced to extensively in the Japanese language, but neither has any true English equivalent, from what I understand. For that reason, they are rather difficult to translate (especially for someone with a fairly superficial knowledge of the language, like me)… Things get even more muddled when we encounter NGE's concept of the soul — as a concrete, "metabiological" entity — and the language used to reference it.