Well the union is now involved. 

She has been told by the union Rep that this isn't the first complaint they have received about this supervisor.

if we have been given all the details, she can't be sacked for that reason.

I was a Manager at W place and it takes 3 warnings for the same thing before you can even consider sacking someone

Well the union is now involved.    She has been told by the union Rep that this isn't the first complaint they have received about this supervisor.

I wonder how many warnings this supervisor has been given then ?