This really doesn't sound any different than the usual problem lactating working women have. How to find the time to pump and keep up your job performance.

First, lighten up on your boss. She's not being unsupportive, but she is a little frustrated. As you are. The issue is really with the facilities. There are not enough adequate facilities for all the working mothers.

Identify what your needs are and bring them to the building manager. Ask your boss to support you in this. You need more lactation rooms, or dividers in the room you have. You need a land line phone in that room and a docking station for your laptop.

21:42 again- I'd add that you will start to need to pump less and less as time goes on- so even if you aren't/won't cut down on pumping now, you will start to as time goes on.

- Consider if you really need to pump this many times a day. It's possible she is skeptical that you really do have to pump that much (I mean, I have 4 kids and I BF/tandem BF all, and I'd wonder if I were your boss), in which case, you might want to consider how you can convey that you do.
- Figure out better lactation room situation. The only one person at a time thing is crazy.
- I'd wonder about the need to have it refrigerated. If I had an employee taking a hour out of the day to drive back and forth I'd be irritated- buy a cool, look up how long breastmilk can be outside a fridge, etc.

Time to get HR involved. They will know the LAWS that protect you as a pumping mother, time for some education for your supervisor...

Also, if you refuse to stop pumping so much, Maybe consider going to part time temporarily?