He was rude. Inconsiderate, ill-mannered (towards everyone but other Slytherins, but he was still ill-mannered to some of them too), crude, and uncivil. She didn't understand why he was this way, although her two friends certainly liked to think because he was a "Death Eater". But let's think rationally, shall we? A sixteen year old boy, a Death Eater, working for Voldemort? I don't think so. I mean, what would Voldemort want with him? He's just a petty little boy compared to other Death Eater's in his army. So, honestly, I don't see him being one at all.
Unless, he wanted revenge for what happened at the Ministry. But, why would he do that? Wasting another precious life (in the case that Draco would fail this hypothetical mission he was assigned) doesn't seem like the path Voldemort would take. He needs (and wants) all the power he can get. Even with the breakout from Azkaban, he would still be hungry for more and more people. It just doesn't seem plausible that Voldemort would assign Draco a mission.
Back to the question at hand though. Why was Draco so hateful? It's not like he's had a bad life. He's good looking (I don't fancy him though), good grades, surrounded by equally good looking and popular people, and has all the money in the world. He's never had to work for anything in his life except for his grades, and he still does the bare minimum of that. So what could it be?
And then it hit her. Hard.
No one is ever that hateful or rude because they were born like that. It's because no one has actually shown them love before. His parents probably didn't show much affection, and neither did his friends. He never has a girlfriend, just a quick shag here and there, but never commitment to one person. He doesn't talk to his friends on a deep and emotional level, just on the broad and non-personal subjects, like the weather or what the homework was.
She felt bad for him. But she would never tell him that. Just imaging the thought of her going up to him and saying that made her want to shoot herself in the foot. Not only would it probably piss him off even more than he already is, it would embarrass him. She learned a long time ago that you should never approach a person in public about their problems. It embarrasses the person, and makes the conversation more awkward than it already is.
She had an idea though. She would help him, with whatever he's going through. In-directly though, because he would never accept help from her.
She was was waiting for the perfect moment to do it. She ran over different theories and scenarios while taking a walk through the castle. Suddenly, she hit a hard wall and fell down on her backside. She looked up expecting a stone or brick wall, but instead a person opposite of her on the floor. It was him, books scattered upon the floor and a broken quill gripped in his hand. She muttered her apologies while sitting up on her knees and gathering his books up for him. After putting them in a neat pile on the floor, she removed her wand from her robe's pocked and repaired his broken quill for him. Placing it back in his hand, and putting his books back where they were in his arms, she stood up and helped him up also.
He stared at her with wide eyes, and she stared back with the same amount of interest and fascination. She never noticed how his eyes were gray with tiny blue specks. He never noticed how her normally wild curls were tamer than normal. They stared at each other for a while, taking in everything they could before someone came and ruined their only chance to fulfill their burning curiosity. Down the hall, echoing laughter and raised voices were heard, the sound bouncing off the solid walls. He closed his eyes before quickly reopening them and placed a smirk on his face. He bent his head down to reach level with her ear, and whispered "Thanks Mud-blood." before straightening back up. Her eyes widened in anger, but before she could reply, he was gone, down the hall where the voices were slowly getting closer and closer. He turned at the end of the corridor, but not before turning around and giving her a quick wink. She closed her eyes, smiling on the inside from not only the satisfaction of helping him, but from that wink that left her wanting more. She opened her eyes again, to find herself standing in front of Harry and Ron. She grabbed both of their hands, and skipped down the hallway, a smile never leaving her face for the rest of the day.