Dana,
I'd say that Alternate Willow precisely displayed potentials within Willow, and that Willow is far more willing to express those potentials when they result in a loving relationship with another young woman than when they result in violence. Actually, I thought the development of the Willow/Tara relationship was very well handled, including Tara's being kind of dorky--an important part of growing up is having relationships with people your friends don't quite approve of and vice versa.
I personally thought that Tara in the fourth season was rather insipid. She was nice, but like a bland version of Willow in the first season, without the latter's wit and humour. At least (having watched the first half of the fifth season so far) she's getting better as a character, the same for Anya.
Murray