If I am following your line of thought correctly, you are saying Kallen has over the course of R2 (and the 1 year gap) learned exactly what lelouch means to her. And now knowing what she knows, she wants to know the reverse. What she means to Lelouch. Because knowing how he feels about her may validate or possibly diminish the value (in her eyes) of what he has come to mean to her.
They have developed multiple possible roles for her to play in his life, but none of them fully enough to say "She is Lelouchs (blank)". However, that having been said...I find this more to Kallen's benefit than detriment. Rather than being possibly important to Lelouch for just one thing, she could become important to him ins several aspects of his life, which gives them a theoretically closer bond. If she were to suddenly loser her legs, she wouldn't become instantly useless if you follow me. She's important for other reasons other than just her fighting skills.