"This is one area where tenure and the union should have no impact." It seems the confusion about tenure is that a teacher can't be fired. Without tenure, a school district can fire a teacher without giving her a reason. With tenure, the district must give a reason for the dismissal, and the teacher has the right to challenge it if necessary.
If she was driving under the influence, the school system will have no trouble firing her. But, I think mrsmusic has a good point. While it doesn't look good, let's at least wait until all the facts are in before we pass judgment.