Kelthaz, how, exactly, is it unrealistic for an addiction to the power afforded by magic to evolve into a literal addiction to magic as a recreational drug?
Re: Willow, she's an extremely insecure character who increasingly latches on to external sources to compensate.
We first start to see this in Season 4, but it becomes crystal clear in Season 6. We also see an extreme reversal to the other end of the spectrum in S7, with Willow being so afraid of fallow.g back into old habits and losing herself that she becomes paralyzed and unable to function. It's actually one of the few things that S7 actually executed well, and it's a pity that her guest appearance in Angel S4's Orpheus derailed it slightly.
I'd also like to ask why a sense of realism is even relevant when we're talking about a supernatural action/adventure fantasy series. Joss never made any attempt to put a gloss of realism on the show as a whole in any way. There was always a certain level of relatability to the show, but that's different from realism. The only time the show went super-realistic was in The Body, and that was a one-time, deliberate decision.