"I’m not sure that we can pinpoint the exact moment that Dimitri fell for Rose. It was definitely a gradual thing that crept up on him (and her!). I can say for sure, though, that he was awestruck by her at their very first meeting. Rose throwing herself between Lissa and the guardians, even when she was hopelessly outnumbered, is definitely one of the most powerful scenes of the series. It establishes Rose’s nature right away-both her bravery and intense devotion to those she loves. Dimitri possesses those exact same traits, and I think seeing that in her was definitely a moment when the world stood still for him."
Richelle Mead answering the question What was the exact moment that Dimitri fell in love with Rose? (Vampire Academy: The Ultimate Guide)
"I spun around, startled. Dimitri stood there watching me, looking both amused and curious. … I hadn’t heard him approach at all. So much for my ninja skills."