It's a tricky situation, but a least it's a fixed term and you do have the personnel structures of a H.E. organisation, and methods of at least resolving some of it.
I've worked in H.E. and Industry, and I'll tell you, HE is far better, but can be very frustraiting as there are lots of politics, especially from the Academics - I'm on the accountancy side but work closely with the Academics, so can see the issues but I have to take a step back from it....!
In industry it can be worse, especially if your boss is a Director - what they say usually goes, the HR team will back them up (even though it's wrong)... crazy. The last two jobs I've left because either the MD or Directors above me weren't all that great and bent the rules to suit themselve.
On one job I even got blamed for a project that went slightly out on 'targets' for delivery of advice to young people - 'becasue money is involved'.... the Operations Director has failed to ensure that the project was delivering the correct number of advice 'sessions', folk in my team found out the problem and were fixing it, but as an accountant, and as there was money involved, it was my fault - no 'boll***'ing of the Ops Director cos they were 'chummy' with the MD - that's when I told them to shove the job......
If you and a number of colleagues (I note you are a Snr Lecturer so this person must be a Principal Lecturer or Exec. level) I'd possibly raise it with the Dean, especially if the teaching load is wrong. There is no reason why this situation should end up in a shouting match at all...a fault on her part I'd say.