Hate on first sight? I'm not even kidding. The moment I saw this woman I wanted to punch her in the face. And as the series progressed my first impression of her was verified.
1. Looks
I don't like her character design. Not a fan of twin-pigtails/braids. The hat looks ridiculous. And while that collar of hers was kinda cute at the beginning of the manga, the style change killed it. Now it looks like she's wearing her grandma's tablecloth around her neck. Plus, it just doesn't go with the rest of the dress to begin with. (I'm won't even start to complain about that slit in her skirt that appeared since round 2 of the WG or her status change to Miss Fanservice.) So, yeah, I just don't think she's pretty. Which makes me even angrier about the fact that every guy in- and outside universe thinks she's hot.
2. Character
Oh, god, where to begin? She's the cheerleader type of character: She's an unlikable bitch, acting all cute towards the guy she has the hots on, treating everyone else like crap most of the time. And she gets away with it! The only times it's mentioned, it is played for laughs. She can act as mean as she wants and everyone will forgive her. That is what I can't stand. I despise this kind of people in general.
I can't even feel sorry for her. When Kaldea was attacked and Dorothy saved a child she said "I'm sorry. It's my sister's fault." ... No, bitch, YOU are Miss-Perfect-and-Undefeated over here. Don't blame it all on your brainwashed sister and expect people to feel sorry for YOU. You were supposed to kill her before this kind of shit happens.
3. Abilities
I don't know which is worse, her winning because of some cheap, overpowered ÄRM or how she just randomly got even more uber than she already is, like in her fights against Chimera and Diana. It's both cheap and boring.
I prefer struggling characters, like Jack. So much more satisfying to watch. Makes a character more likable, too.
To sum it up, she's not attractive, she's an unlikable bitch and a Mary Sue.