Aw, well thank you with "an authority." Basically this is an insecurity thing, insofar as the moment someone says I'm good at something is the moment I stop being able to do it because then there is a possibility I will say something for that label to be retracted.

I think that Anya's arc is actually not entirely easy to parse, but a lot of this goes with something that I've thought about a lot, and taken some inspiration from Maggie and beer-good-foamy and lostboy-lj about (among others), which is that the show very deliberately plays with tone. Anya is a comic figure because she's a background character, for the most part, and that is because Xander is a comic figure because by s4 he's mostly on the periphery of Buffy's life emotionally. Spike, in s4, while he's totally chipped and powerless to do anything evil (except in The Yoko Factor/Primeval), is generally treated with the same kind of light touch. The main reason she is treated as a joke is because she has no power, and so the gang don't have to deal with her past. This is weird, but I think that it's part of the show's strategy: the tone reflects how characters perceive her, especially Buffy, and Buffy sees Anya as a bit of a fly buzzing around the outside of her life.

I think that the reason that Anya sides with Buffy & Giles at the end of s6 is not because the writers were ignoring Anya's demonness, but because they were actually *demonstrating* that Anya's allegiances have changed. There is a strong case to be made for Anya having one of the cleanest, clearest arcs within the season finales (or, more precisely, the season-ending conflicts) --

s3: GD1: Anya asks Xander to leave with her rather than die in the apocalypse; Xander stays, Anya leaves him and says she hopes he dies.
s4: Primeval: Anya tells Xander she loves him for the first time, reassures him.
s5: The Gift: "Usually when there's an Apocalypse I just skedaddle! But now I love you so much I'm having inappropriately timed sex and thinking of ways to fight a God."
s6: from Villains: "I'll help, but I'm helping Willow." She is on the side of the good guys WITHOUT requiring a commitment to Xander in order to be helping with the world; her personal connections to the gang and Willow & Giles in particular drive her involvement.
s7: Chosen: she stays and fights, because, as she says in End of Days, "When it matters, they fight. ... So I guess I'll keep fighting too."

The reason Anya has to be a vengeance demon in the s6 finale is that we need to see her commitment to goodness actually transcending her tribal connections; as she says in "Selfless," accurately I think, "My whole life, I just clung to whatever came along." She first was actually evil (The Wish), then wanted to be evil (Doppelgangland), then through the finales she went from indifference to fighting for Xander to fighting for her friends, while officially on Team Evil, to finally fighting for the abstract good in Chosen. <3 Anyway!

I do agree that Anya's interest in money was her own and not encouraged by the others, but this is also a form of "self-lessness" -- her capitalistic furor runs in parallel to her total adoption of the vengeance demon code of ethics. She loses her independent values and takes on the dominant values of the culture, and then neglects anything she thinks is irrelevant to those. The money thing originated with learning that money was the goal in the Game of Life (from Xander!) in "Real Me." She takes on entire systems wholesale, rather than being able to deal with nuance, at least early on. And I think that Anya's hypercapitalism actually ties in with her huge excitement at the impending marriage, some of which does not really have to do with Xander at all IMHO but with just having all the things a person has to have (see her in The Replacement, demanding an apartment and a puppy because SHE'S GOING TO DIE SOMEDAY).