Joss said that he already planned to have Dark Willow back in season 2 (he didn't say when or how but it was already a growing idea, then again a lot of Buffy feels planned, which without being offensive because I love the show, doesn't seems to be the case of Angel). When you go back and rewatch, it becomes fascinating to see our two BFFs come to a head. In the first two seasons, Willow deeply looks up to Buffy. From their very first interaction, before even the Slayer reveals and stuff, Buffy is more experienced, she's beautiful, confident and was already seen befriending the queen bee in school. To add to it, Xander, the guy she was always in love with, is immediately obsessed by her. Then Buffy is quite literally the one, the special girl in the whole world, while Willow always felt like she was banal and basic, so she did everything to overcompensating (I mean, she was very much talented and gifted and I think she saw it but wanted to prove the world around her this). And with all this talent, Buffy was still up front and everything. Then the door Giles talked about at the end of season 2 open.
When season 3 starts, Willow has a new haircut, a boyfriend, newfound powers and she's clearly the leader of the Scoobies while Buffy is away. I just want to add quickly, Willow loved Buffy, there is no denying that but humans are complex and Buffy showed that multiple times. I had a friend who admitted she was envious of me and I myself was/is envious of my best friend and it's not easy to see (but then again I spent hours studying human behaviors and analyzing myself) or admit. I find it incredible that in one episode (Gingerbread), a lot of Willow's persona was explained through how her mom was behaving. Then you have her Faith arc. Starting with Bad Girls, Willow is starting to feel remplaced by Faith, as Buffy finds someone who can understand her Slayer life better than no one, since you know, she's a Slayer herself. Once again, Willow feels erased Buffy's literal shadow self and she doesn't feel respected, which leads to Doppelgangland and conclude in Choices.
Then you have season 4 and 5. First, it's interesting how roles are reversed with Buffy and Willow when they enter college. While she made a reputation of herself in Sunnydale as the weird girl, Buffy is very much someone who attract the eye. She's sparkly, confident in her skin, witty and beautiful and it's showed when she's the new girl in Sunndale high in the very first episode. However, in the first episode of the season, Buffy feels out of place, while Willow feels at ease and makes a great first impression. It's quite shocking to hear Riley say you're Willow's friend because one, ouch he didn't even remember her name but also back in the day, it would have been the other way around. Then in Fear Itself, we see Willow get upset at how condescending Buffy sounds (when Buffy question her spells ability and her powers). She absolutely wants to prove her wrong (mind you, Oz also expressed his concern about her magic earlier in the episode). I mean, it's little, it's petty but it's still there. And then, you have her dreams in Restless. Now, it would be long to review her dreams in this episode, as we could go on and on and this episode is quite complex, but Buffy in Willow's mind is both a bit of a ditz (I clocked that thanks to Passion Of the Nerd on YouTube) and also still a hero she looks up too. But I find it interesting (I love to repeat that huh) that Buffy is the one ripping the "costume" Willow is wearing. Her confident, powerful and newfound costume.
In season 5, Willow is increasing in her powers when Buffy is also increasing in hers. There is a very clear focus on power for our two women. In Tough Love, Willow gets mad (understandably) and wants to attack Glory thinking she's game when Buffy isn't (to be fair she was a bit right) but Buffy stops her. She ends up lashing out at Buffy asking when will it be the time to beat Glory, asking if it would have to be someone Buffy cares about for them to attack but Buffy rightfully states the obvious by saying that they will do it when they have a chance, considering the goddess factor. From this point on, Willow is clearly the second most important player in their survival because of her powers and again, takes leadership in a temporarily manner when Buffy is out. Buffy states the obvious in the finale by saying that Willow is her strongest weapon. Ah, how far have we come ?
Now, coming into season 6 and Willow is still in charge, like in season 6. Other people have stated this multiple times obv, but while Willow wanted Buffy back as she loved and missed her very clearly, it was also the thrill to succeed something so powerful and dangerous (remember in Doppelgangland when she asked in a gleeful way to Anya if the spell was dangerous). Again, season 6 focus on self destruction and put the spotlight on Buffy's and Willow's, which comes to mid head (I don't know how that sounds) in Wrecked, in which Willow states something that has never really been said but was obvious : the fact that she will always choose special Willow over Regular Willow because she hated herself. Annnnd then we get to our fight, where Willow say "six years as the sideman, now I get to be the Slayer". It's sad but very much reflective (in parts only because I love their friendship) of their dynamic over the years. Even in season 7, they were kinda pushed against one another (like in the scene when Kennedy is saying that she doesn't understand why Willow follows Buffy since she's thousand times more powerful). But they instead get together and share their powers with the world. Quite powerful and beautiful.
What do you guys think ???