I belive that Karen died an unnatural death. In the following paragraphs i'll explain why I belive this. One reason is she made some people mad. She mad the company mad also.
First, she made some people mad. She made Winston mad at the union meeting by trying to shut the plant down. If the plant shut down he would lose his job and others would lose their job also. She made the preacher man that worked with her mad by not scanning her self on her way out. Someone contaminated her pills and Winston and the preacher knew she was taking them but, Winston knew where her pills were, that's why I belive that they may have killed her.
Another reason is that she made the company mad by trying to shut them down. She was doing this under their nose and she knew that if they found out they would fire her.
They found out because of the of the union meeting. Another clue is that someone contaminated her pills. After she turned her stuff into the doctor they went to her house and said that it was contaminated and took it apart and when she said her pills were contaminated the boss said that couldn't happen.
That's why I belive that Winston contaminated her pills. So may the preacher rammed her on the road so she couldn't shut down the plant. Maybe the company contaminated her pills and hired somebody to kill her. So that's why I belive that she died an unnatural death.