Here's hoping no one finds out what that sword can do. I'm with Spike. Willow has little control over her emotions. Or rather she feels that her emotions are more important than everyone else. And if they aren't giving her the attention she thinks she deserves she'll do a spell. It's all about her pain, her feelings, her thoughts. She proved it already with all the spells she did. One of which almost starved Buffy to death.