Basically, Willow has a vision of Tara dying and Buffy dying and is told to make a choice to “save one, you cannot save both” and she’s determined to save them both anyway.

So she sacrifices herself to save Buffy and Tara and she dies and gets sent to hell. Glory was able to take over her hell dimension once again and the other two hell gods are pissed that Willow’s there since they think she’s the one responsible for Glory’s return (and their subsequent loss of power)

Willow is determined to go back home, but time is very different down in the hell dimension and Willow essentially spends centuries trying to take on Glory and defeat her, even though the other two hell gods give her a warning that if she somehow managed to return to Earth, she and Glory will share the same entity. Like Ben is Glory.

To appease the hell gods and prevent another apocalypse, Willow submits herself to Glory’s eternal torture so that Glory won’t try to reign hell on Earth.

Willow does eventually come back to Earth, courtesy of Cordelia and the Powers That Be, but has no memories of her previous life.

What do you guys think?