I see. It's not at all cool that your manager gets to hang out in the back, probably breathing freely, while you're out front with prolonged oxygen deficiency. I'm not trying to get in your business, @jacobtothe, but just out of concern for you, maybe you could:
(1) Ask her to "trade places" with you for ONE WORKING DAY. I bet she wouldn't be able to withstand it. Or, at the very least, she'd be a better ally for you with greater empathy; and/or
(2) Go broader. Link up with an appropriate/related national library association, and see who else is having difficulty. This is not 'making trouble.' It is highly abnormal to make suffocation a way of life! This is advocating for your health, and avoiding brown lung, or bacterial pneumonia.
RE: Do you work in an environment that "requires" you to wear a mask? 😷