I agree. While widows & widowers are often lonely enough to sleep wiith someone, i don't think Willow would choose Kennedy. Willow was clearly not ready; she had to be backed into a corner.
Willow had a type. Hostile uber macho was not it. Even if you include men in the calculus, Oz was manly but gentle. Xander was flawed and a mess but also gentle and very caring. Tara was one of the kindest, most caring people ever. Buffy, her friend, was not a bully.
Kennedy was a large, steamrolling bull in a china shop crushing what she could not manipulate.
I have major reservations with Willow but no one deserves Kennedy.