What's important about considering Willow here is that the majority of her life has been about The Rules. The go-to-bed-early, brush-your-teeth, do-your-homework, obey-your-parents Rules.
Willow has always had a really clear understanding of these rules. She's always committed herself to the carrying out of them to the letter. To the letter. Deviation from The Rules for her, is always seen as being "bad". Doing something she feels is wrong, doing something that will, eventually, make her a "bad" person.
I think that what we've seen with Willow's maturing role in the show is that she has accepted and integrated these rules into her life. For better or worse. And the heartbreaking result of this is that she's positively broken by them, ultimately.
**
1) - The Family Thing
Willow grew up as an only child in a family who hasn't loved her properly. Her parents have literally ignored her for most of her life, and yet she has strived to fulfil the expectations consciously or unconsciously placed on her, despite the fact that she is aware of the lack of parental contributions to her life.
Makes me grateful that my mom's not interested in my
extra-curricular activities. Or my curricular activities.
Her reward for playing by her parents' familial rules? To be totally ignored by them. To be punished by them (the episode Gingerbread plays this out perfectly.
This is the first time ever I've done something you don't like
Willow's "reward" then, is tainted by the fact that it's not a reward at all. The first time her mother notices her, it's to berate her and punish her. Being a good daughter, it seems, is to be a silent one, one who doesn't live. A daughter who isn't alive in the sense that we recognise, but one who plays by The Rules.
***
2) - The School Thing
Willow is a good student. No, she's not just a good student, she's the best student. She works hard, turns up to school, respects authority figures (even when she knows they're wrong) and excels in every subject she takes. She's playing by The Rules. She's doing what she's supposed to do, surely? The episode Choices plays this out perfectly in that Willow makes a decision to stay in Sunnydale, despite the whole of that episode focusing on the various places around the world where she could potentially study.
But she stays.
Willow: Must be tough. I mean, here I am, I can do anything I want. I can go to any college in the country, four or five in Europe if I want.
Buffy: Please tell me you're going somewhere with this?
Willow: No. (hands Buffy a letter) I'm not going anywhere.
She stays because her sense of loyalty to the "fight between good and evil", and her sense of friendship causes her to give up a glittering future.
Her "reward" for playing by The Rules? UC Sunnydale. Making do. Writing her own curriculum. And a best friend who begins to drift further and further away from her during Season 4. No wonder that Willow herself drifts away from societal codes in Season 4 and brings her to her next trial.
***
3) - The Tara Thing
Tara. Willow's relationship with Tara is possibly the one enlightening feature of her life. Going against these so-called Rules, Willow gets involved with another woman. This time, she lets her heart lead her head, and finds the one thing in her life, possibly, that gives her fulfillment and joy. And peace. I don't need to go into the ramifications of Willow and Tara's relationship because I feel that other people have already said it in numerous threads on this board, and far more eloquently than I can ever do.
However, the main thrust of Season 6 has shown a Willow who breaks rules. Tabula Rasa, Smashed, Wrecked...all these episodes show Willow's backlash against the restrictions placed upon her thus far. The eventual dessimation of her relationship with Tara proves to her that in order to regain the trust and love that she once had, she must go back to The Rules. Those bloody, slow, painful things that held her in place all the way through Seasons 1 - 3.
WILLOW: (firmly) No. I can't. (to Anya) If I start, I ... I might not be able to stop.
And she does it. She does it because she wants to prove that she can be worthy. And in proving herself worthy, Willow has made a conscious effort to return to The Rules, because she knows that that is the only way she'll be able to win Tara back. And her need for that affirmation of a change of behaviour is paramount in the episodes following Wrecked. She's returned to following the codes of society in order to make a statement to her lover. And she does it. She succeeds. Far be it for Willow Rosenberg to fail at anything. She never has before. And this is no different.
TARA: I get it. I-I really do. But it's time to work without the net, Will. (Willow looking anxious) You know, I don't know if you noticed, but it actually did get bad in there. Really bad, and ... and you still said no.
Tara smiles, goes back to her task. Willow slowly begins to smile too.
The eventual reunion of Willow and Tara makes it clear to Willow that by adhering to those rules, she can make things right again. Not with magic, not with running outside of the codes in society, but by following the steps someone else has prescribed. No, by returning to the strict ways of accepted behaviour that formed her teenage years, she feels sure that this time, the reward will be worth the struggle.
So then, what is her "reward"?
Clearly, Willow and Tara reunite. They celebrate their love for one another and make their commitments to the relationship anew. We, as the audience, invested in Willow as a character, get to see her experience the one true happiness in her life.
But that's not all. Nope, not by a long shot.
See, the "reward" brings with it the ultimate punishment. For someone who has realized the error of their ways, and turned back to set things right, there can only be one solution. Tara is taken from Willow again. And this time, it doesn't matter what rules Willow employs, she's not allowed to get her reward. Again, the reward for her is punishment.
***
So what's my point then?
Well, the point is that I can't blame Willow for what she does. I can't blame someone who has been beaten down for most of their lives, been restricted and honest and obedient and conscientious. I can't find it in myself to blame Willow for eventually turning to the darkness. I think that the Tara situation is the turning point in the evolution of her character.
Perhaps the biggest thing Willow ever did was to give up her magic. Perhaps the biggest sacrifice Willow ever made was to apply those life rules to herself once more, and revert back to the kind of person she hoped Tara might want. And in making this sacrifice, what does she get?
She gets punishment. She gets pain. She gets sorrow. Yeah, she gets her heart ripped out in front of her and you know, I can't blame her for wanting to destroy that heart so she never feels anything ever again. I can't blame her for that.
So when you want to blame Willow for what she does, think about The Rules. Think about how everyone else around her gets to break them without repercussions. Think about how Buffy, Xander, Anya and Spike have persistently managed to get away with metaphorical murder. Is it so wrong then, to wonder why Willow can't get away with it literally?
I don't think so.
----------
Hey Grrrrlfriend! Yoo hoo! Over here! It's me...Flaming Joel!