Hmmm...as to the first question, I can't think of if or when she just said "I love you."
As to the second question, I think she first realized it in TOGoM when she thought Clark was dead. I really do think the idea that she would never see him again allowed her to confront the feelings that she'd been ignoring: specifically, that she was falling in love with him, despite the fact that they hadn't begun dating yet.
