If we look at the fruits of Anya's life, we see she repented (turned from) from her demonosity, and she fought against evil and for good, which would be seen as serving God in a "Those who are not against us are for us" kind of way.

I can concede that.

Do we know of anyone who has died and gone to hell besides Darla?

Angel went to Hell, but he didn't die. He got sucked into Hell. Buffy went to Hell with Lily/Anne, but she didn't die to get there. Was that place Skip guarded, where that Billy character was a Hell?

Angel, Billy

Angel was already dead when he went to hell.

No, he was undead.

And yet. . . not alive.

Still, dying wasn't what got him to hell. His animation status was unchanged.

I recall a lot of use of the words "hell dimension", I thought they were trying to shy away from the use of the christian "heaven" and "hell"

In a Christian universe, Anya goes to purgatory. That's the place for righteous unbelievers, right?

If it's binary -- heaven or hell -- I think it's hell because she never repented, which makes me sad.

Isn't purgatory only what Catholics believe?