Boss Signing off impossible plans, calling others incompetent for not being able to implement them.

So, I have a problem at the moment with an ex boss of mine who I always had a bad relationship with. Essentially she's the kind of person who is always right and you are always wrong and if you dare to challenge her when she is wrong and you can prove it, she will talk down to you like a little child. It always used to create a lot of tension in our department because challenging bad policy or bad decision making was basically only going to end up with a big argument.

Anyway, she was moved aside to another department and we've not had much interaction for two years. However she is now in a more senior position and has singed off some plan for changes to the way we conduct our day to day business. As part of that business, we use some very specialist software for our industry that doesn't allow for us to implement what she has signed off two months ago.

The team tasked with responsibility for implementing this is one I am leading, We only found out about it today and have straight away let the powers that be know that what we have been asked to implement isn't possible on our systems and we have come up with some proposals that would work that are close as possible in terms of what was originally proposed based on our knowledge of the systems. We have also had this confirmed by an independent party and our third party support company who supports this specialist software. They back up my teams view and have suggest we take it to our senior management team to get them to rethink.

My ex boss has since literally gone off on one big style and told us that if we are not capable or do not have the skillset, experience or knowledge to implement something that is possible, then this is a real concern for her and maybe it means that we are not very good at our jobs because it is possible and that anyone who was up to the job would do it. This is obviously a deflection tactic to say it's not the plan that is the problem, but the people implementing it.

This is typical of the manager in question. As most of my dealings over the past few years with her, she has never ever admitted to making a mistake or getting something wrong. Now she is essentially calling me and some of my colleagues openly incompetent for not implementing an impossible solution that she should never have signed off on, And she has made it clear she will not be backing down and has the support of senior management who had her advise on technical aspects of the plan.

Since then we have called senior management in to explain the issue and that we are being put in a very difficult situation. They have spoken to her and she now wants to be in all meetings about our work. We had the first one today and all we had was incessant interruptions and commentary from her finding fault with almost everything that we say as she is determined to try and portray us as incompetent in front of senior management to make us the fall guys.

Does anyone have any experience of how to handle this? Effectively this manager has gone completely rogue and couldn't give a damn anymore about what the business needs and has gone to all out self-protection mode at the expense of everything else.