What I meant when I used the word "lukewarm" was that although she is clearly headed in that direction (and for the right reasons, as you point out), Elizabeth is not in love with Darcy yet. I think this is more evidence against the idea that Elizabeth was secretly/unconsciously/subconsciously in love with Darcy all along.

He: You must allow me to tell you how ardently I admire and love you!

She: Thank you very much. I like and respect you, and oh, yes, I feel a real interest in your welfare!

I don't think so. As somebody once said, the only really acceptable answer to the words "I love you" is "I love you too" (even in JA's day, IMO, though they might have expressed it a little differently!).