I've given the Treasurer a deadline by which the account has to be corrected in order for us to prepare next year's budget.
As a side note, the Treasurer is very defensive about her position - I made one report request of the school's Business Manager in order to get some final numbers for one of our Committee Chairpersons and the Treasurer accused me of trying to do her job.
I wonder why she is so defensive? Considering that you have the background to help her, it just doesn't make sense. I mean, let's see, she is a volunteer trying to help out (like us all, right?). She has been given a position she doesn't know a lot about (and we've all been here before, right?). She doesn't do the job very well (but on nomination night last year, how many people said "Oh, it's really easy and we'll all help you?"...right?). You have the skills to help her (you did say an 'extensive background' and I gather that means school or some other form of accounting education which the average joe might not have...right?) You issued a deadline and then went over her head (and she still doesn't know how to fix the problem and now must be feeling awful, frustrated, mad, useless and OMG! maybe even defensive... right?).
I know, I know, you're busy and it's not your job.
Take a couple hours a week and help this gal out. It's the right thing to do. After all, it sounds like
YOU are the resource you've been looking for to help her. Teach her how to do the job right and who knows? Maybe with some training and encouragement, you won't have to train another one next year.