In my opinion, no.  She's not evil.  In fact, I would argue that if she were a man she would be seen as a hero and there wouldn't have been any need for her to die at the end of the story.

It seems to me that Kriemhild's only motivation for doing any of the things that make her look evil is revenge.  She knows that Hagen and Gunther are responsible for the death of her husband.  Given that this is true, why should she not want to kill them?

During the time when this epic is set, defending one's honor and avenging insults was an important part of life.  If this is so, how can we say Kriemhild is evil for seeking revenge for the death of Siegfried?