Reimu just being a complete asshole? I don't think that's accurate. Like many other Touhou characters, her duty is paramount to her. In this case, her only function is to resolve incidents and defeat youkai. So yeah, she's gonna run around beating up people, and she's going to be tired of their shit.
But the duty is not all there is to her. We've seen her other face a million times: at the end of games, with the fairies and Kosuzu, and even through Miko's power. Reimu is someone who will accept absolutely anyone, who values her friends, and who wants peace more than anything. She can't admit any of this at all, even to herself, because it is in direct opposition to her duty as the incident resolver. But it's there, and Marisa calls her on it multiple times.
Reimu's neglect of being a proper shrine maiden is the main beef people like Kasen, Rinnosuke, and Keine have with her. To me, it's simply because it's completely irrelevant to who she is, other than the flavor of her powers.
The greed though, that's just her being a typical Gensokyo jerk.