Agreed with Elu!
Margo- I saw both of those occasions as Fleur being fed up to hell with people just obsessing over her looks and never trying to get to know her (especially her date, who if I remember correctly was just nodding and staring vaguely when she was trying to have a legitimate conversation) and Ron, being some kid who just drooled over her constantly- when people view you as nothing more than what you look like it's quite irritating. I mean, she's this strong, independent, intelligent and ambitious seventeen-year-old young woman and this fourteen-year-old kid is just drooling after you and obsessing with you- not to mention him being Harry's best friend, and I believe Fleur was pretty irritated with Harry.
I mean, from her perspective, all she knows is what she's heard, and though I don't believe she is some newspaper or gossip obsessive person, she shows up at this school determined to work hard and prove her worth and some fourteen-year-old kid is presented as her competition. She must have found that offensive, both as an insult to her ability and to how hard she worked to get into the Tournament (seeing as she knows that SOMEONE cheated to get him in the competition, even if it wasn't Harry).
All in all, I could very much relate to Fleur. She's a young woman trying to prove herself, and maybe she does get a little too irritated by Harry and Ron but hey, she's allowed to have flaws.
But Fleur also falls into my character type. I just really, really love her. And like you said, FANTASTIC character development.