Nonono.
The whole point of Willow turning white was that she was a powerful witch and that she could use her powers for good. Ever since Willow started using witchcraft, it was said, many times, how powerful she was. She got TOO consumed with the magic and got addicted to it. She stopped and everything was good. Then good ol' Tara had to get shot, so she went all crazy. During season 7, she was too scared to use her magic because she thought she would go all evil again. However, she did the slayer spell, her powerfullness(not a word) didn't make her turn to the darkside; but the good side.
She isn't a Goddess, but is a GOOD POWEFUL Wicca. And she didn't pass out, she just fell over because it felt that damn good. It probably felt like a HUGE orgrasm.
Well, that is how I always looked at it.