Yes, those were definitely nerds in the bad old dual studious/inept sense. However, Willow Rosenberg was much more central to the series. Wikipedia actually says, "Willow is a shy and nerdy girl with little confidence," and, "Willow is presented as a bookish nerd with considerable computer skills, dowdily dressed and easily intimidated by more popular girls in school."

buffy.wikia.com says, "Willow started out as a meek and largely unassertive computer nerd, but eventually grew to be a powerful and authoritative individual," and, "In her early years at high school, Willow is a shy, naïve nerd with a light, risqué sense of humor. A member of the Math, Science, and Computer clubs, she is the person to go to for tutoring help. Willow is ridiculed by her more popular classmates, including cheerleaders Cordelia Chase and Harmony Kendall." It includes the corporate explanation of the shift in Willow:

Joss Whedon explained, "The incredibly nerdy clothes that she's wearing, you'll see her wearing for exactly one episode, because [the network] kept sending us memos 'You must make her more hip. You must make her more cool. You must make her more... like Buffy' which confused me because, you know, I wanted to do an ensemble show and ensemble means that people are different. Besides, I think that outfit's really cute."

Which suggests that Whedon wanted to sustain Willow as more of a nerd in all respects, but the suits said no, and so this is why Willow became more of a Hermione and less of a female Anthony Michael Hall. Harry Potter came out in 1997 and Buffy (TV series) came out in the same year. Even though both the HP books and Buffy continued for many years, the characters were sufficiently established early on that my guess is that there was minimal influence.

Thinking of female nerds, The Mummy's librarian pops into my head. Played by Rachel Weisz. Some degree of social awkwardness, but not really all that much. Definitely studious - knows enough to wake the antagonist.