It's no fair.
I read that Joss was originally going to bring Tara back in Season 7 in an episode where Buffy could make one wish, and she wishes for Tara to come back for Willow. Although I would have loved to see that, I can understand why Amber didn't want to. It wouldn't have been right, especially after everything Buffy went through when she was resurrected. But just imagining Tara being back with the gang and being there for the finale!
