Think as a business man. You are your own (entity) small business and therefor fully in charge of your furture. If you really want this position you need to take charge and succeed.
You must find a way 'round that train-wreck of a boss that's standing in your way. Do what ever is needed to make your business (you) move forward and prosper in spite of any obstacle.
If there is no other way short of having her killed-off, prepare for plan "B": New job.
