It is at this time (whilst having a hard time dealing with her emotions) that Willow realises how to turn Amy back from being a rat (by using a “Reveal It” spell). For a time, Willow has a new friend to practice magic with, who unlike Tara, does not have any morality concerns regarding magic (and its use).
Amy helps lead Willow along a forbidden path: using magic for fun/pleasure. When this does not prove to be enough (for Willow), Amy introduces Willow to Rack (a warlock), who helps her experiment with black/dangerous magic: eventually resulting in Willow summoning a demon. Shortly after, things come to a head when Willow nearly kills Dawn (Buffy’s sister), and Willow is forced to admit that she needs help with her addiction to magic. It is here that we find the concept of a “spring clean“, when Buffy and Dawn help Willow remove all magical items from Buffy’s house (such as candles, charms and crystals), thereby removing temptation (so that Willow stands a better chance of going “cold turkey”). For a while, the tougher approach works, and “old reliable/nerdy” Willow is back (e.g. using computers for research).