Willow didn't figure it out until Xander's date ended with a stab wound.
Xander was still a demon magnet.
Last year Giles couldn't see how much they all needed his help, both before and after she brought Buffy back.
And Buffy and Spike, well . . .
She'd done the spell to get over Oz. Two weeks later she'd clasped Tara's hand, creating magic with her.
Let the healing power begin. Let my will be safe again. As these words of peace are spoken, let this harmful spell be broken.
What if breaking her spell wasn't as simple as just chanting a counterspell?