When you say she is 'frustrated...is t possible she is just done? Full? Not interested in nursing right then? In other words, is it possible your baby’s behavior and your pump out put are not exactly in sync nor explain each other?
Because a baby this age will very typically nurse for short amount of time some of the time ,and be distracted/fussy/popping on and off etc. Many times the 'best' as in longest nursing sessions happen only when baby is nursing to sleep, at night, or having ‘good morning’ nursies in bed. If a mom is concerned about low production, the distraction at other times may look very much as if baby is 'frustrated' when it is in fact normal. Also weight gain ‘velocity’ typically starts slowing down at this age, sometimes quite dramatically, which also tends to get everyone worried, unnecesarily.
It can be quite difficult to maintain adequate production when pumping instead of nursing part of the day, and it sounds as if you have a very demanding job, so I am not doubting you, it's likely your production has gone down somewhat and what you are able to pump may not be adequate. Certainly your pump output has gone down. But wasn’t it extraordinarily high at it’s best? 25 ounces per day is what a mother who is eping – not nursing at all-would love to see. But you were nursing at the same time, at least part of the day, or am I not understanding?
It sounds as if your baby's weight gain has been normal and your baby is not acting like baby who is hungry-a hungry baby will nurse and nurse, trying to get another letdown, desperate for more milk.
might it help to consider some quality of life things here? Many mothers find that, if possible, they do best with a less demanding work scedule in those short months of young babyhood. And/or, what about making that time at home more relaxed? All this pumping when you are home with your baby may be cutting into time you could be spending sleeping with, snuggling, playing with and yes, nursing your baby. Some mothers find that what works best for them is to have baby get formula as needed when mom is at work-you could still keep up your current pump schedule at work, take galactagogues as you like, but when you are home, relax and love your baby, even if that meant slightly more formula than expressed milk for baby the next day.