I had this same issue, to resolve this problem i resigned and in exit interview mentioned all this. A week after my departure that manager was demoted. Karma comes around in the end.

You definitely need to have this all in writing. Write an email explaining that people are asking for training and that the company will lose productivity if people can’t use the software effectively. Note that she cancelled the sessions and has advised you shouldn’t update the user manual and that you explaining each time to each person with a question is a very slow and inefficient way for everyone to get up to speed on the changes.

This how it begins. Start updating your resume. You’re boss is replacing you this week.

Even if this is a tactic to get the person fired, it seems like no one being able to use the software would be a rather major problem with OP gone.