Maybe you should talk to her and explain the situation. You could also call and put in a request for an accommodation. Going a few minutes over your 10 in this situation would be a reasonable accommodation. I think unless things are communicated you can’t assume people will fully understand something unless you tell them. In this situation unreasonable might be a little harsh. It sounds like she’s not telling you that you’re not allowed.

Damn, your manager seems very unreasonable. I can't even fathom that you're trying to squeeze pumping into a ten.

Take into account getting off the floor, gathering your pump and bottles, setting up and then breaking it all down, storing your milk, and rinsing pump parts... I sure wouldn't have enough time to pump a whole feeding.

Also, take into consideration that if you're not pumping as much as you'd usually be feeding, your supply could drop. By not pumping or feeding, your body thinks that baby is not as hungry, and produce less.

Maybe she needs a reminder that by law you are allowed a reasonable break to adequately pump in a private, sanitary area that is not a bathroom. Employers are not obligated to pay during these breaks, so maybe she'd prefer you clock out for it? State laws may have more protective restrictions in your favor.

Maybe there is a schedule that better fits with your pumping schedule?

Lastly, there is always corporate, or PCC. I'm licensed, so I've never dealt with them before.

I wish you the best of luck and a reasonable outcome.