The reversal of wishes?

[Xin Rong]

In series 3, the wish Giles says that once anya was defeated all her wishes would be reversed however we know from episodes like hell bells that not all of her wishes were reversed, why is this?

 

[eponinethen]

Yeah I thought that was a bit strange. I mean she has affected the world a lot, apparently, so I doubt all her wishes were reversed.

 

[SpikedBuffy]

Well, and in this episode, we were getting a glimpse of what Anya was like. The destruction that she caused. Even if all the wishes might have been erased 'physically', mentally, we were still able to watch them.