Susan, I was never a specific wedding coordinator, but as office manager for a beautiful old church in the Boston area, I did deal with some weddings. The people involved were totally mellow, so I was pretty lucky there. My advice (because I *did* constantly have to tell people that they could not could not have the run of the place, which was often challenging) is to just stick to your guns, keep repeating that you don't know about the fridge, the this the that, that the groups involved have a right to be there as well. Does she have a contract of any kind?
Just stick to the facts again and again, and don't let her get you riled up. Let her know (preferably in writing) what her responsibilities are.
Signed, BTDT.