User blog comment:Mr Easter/Could Kuina be tashigi/@comment-3125914-20131215072145

Disagreed.

If I remember well, her coffin and her grave were shown. Kuina is clearly dead to me.

As for why Tashigi looks so much like her, well just coincidence. Also, to put Zoro into an uncomfortable situation and maybe some comic relief.

Besdies, even in real life is possible to meet someone who looks similar to you and be completely unrelated.