But rememer: Willow was once the shy, nervous girl. Then Buffy came and together with her she rises. I don't think Willow would ever got so powerfull without Buffy. I just don't think that Willow would have got out of her "silent girl" role without Buffy and the things she experienced with her. Buffy had this "common just do it"-mood still from the beginning of the show. Willow hadn't. Still I love her because of other character-skills she has and noother in BTVS. 😀
Still in the first forty eight hours of Buffy approaching Willow, Willow carpe diems with the first guy to hit on her, asserts herself against the vamp that tried to capture her and Darla, shielding Jesse's body as she does so, talks back for the first time to Cordelia and messes her up with "Delete=Deliver", reveals her hacking to a school authority and others to provide the city plans, participates in the fight and throws Holy Water in Darla's face to protect to Giles.
IMO, Willow was desperate to break out of the confining box that her parents and the Cordettes put her in and she wanted to have something in her life other than studying, tutoring, following Xander around like a lovesick puppy and sitting in an empty house. In the story, Buffy was a big part of providing that. However, I don't see why Willow couldn't have had a similar growth-arc for confidence by getting special Slayer skills and having Giles take an interest in training and developing her and experiencing that there are bigger things than her pre-S1 life.
I think Willow would've been one of them slayers that got killed after about 2 weeks. She had'nt the strong personality that Buffy had. Even if she did survive the first year, the Master would have destroyed her.
Having contempt for Willow is your prerogative but I don't see how the circumstances of Prophecy Girl would change much if Willow was the slayer.
It was prophecied that the Anointed One would lead the Slayer to hell. I do see Willow, crushed with responsibility to save the world and scared of disappointing Giles, following that prophecy instead of Buffy's decision to quit slaying to save her own life.
The Anointed One leads Willow into hell like he led Buffy. The Master drowns Willow like he did to Buffy. Xander would still be Willow's friend like he was Buffy's and if Angel was really interested in providing information (even in Prophecy Girl under duress) instead of just flirting with Buffy, Angel would lead Xander into Hell. Xander saves Willow's life as he did Buffy's with CPR.
Slayer Willow, like Buffy, feels determined to destroy the vampire that killed her and to save the world. I know that would be the case because even by
I Robot, You Jane entirely mortal Willow felt the need to fight Mollock armed with nothing but a fire extinguisher for kidnapping her and his evil acts. Willow kills the Master, like Buffy did, with her slayer skills and her ability to not get hypnotized learned by her near drowning in hell. The end.