Hi MC-
First, whatever you can offer her in the way of breastmilk will be great. Some it better than none.
I know how tough it can be- I am a wedding photojournalist and was breastfeeding at the same time! My clients knew I had recently had a baby and were excited to hear updates about her. I let them know that I was breastfeeding and that at a point in their day I would need to take 15 minutes to pump. They were all great with it and even reminded me as I was shooting that I needed to do this.
When the days were super tight (not a lot of downtime, or there wasn't a place for me to handle this that wasn't in the way of the women, I would plug my pump into the cigarette lighter outlet in the car, jump in the backseat, and just pump there. I was really self conscious at first but with my back to the window, a nursing bra that just flipped down, and my (loose) sirt hanging over the flanges in the front, you couldn't see anything at all!
Also, the Medella pump and style has a built in cooler in the bag so I would bring mini ice packs and just store the milk until I got home. Anitbaterical foam soap in a travel size and medella quick wipes are wonderful tools for this. So are the baby shades in the back seat to add to privacy.
However, I think if you mention to your contacts that you need to pump before or after a meeting you will be surprised at how accomadting people can be. And, by law, it is your right to continue to pump when you return to work. And, there is always the car.
As for the formula, of course your baby will be fine. My daughter was supplemented as well because my body was having supply issues even before I returned to work. And, your supply WILL go down if you are not pumping during the day, but, we all do what we can for as long as we can and in the end, the babies are great!
All the best!
C.