Your ped is way off here. A breastfed baby does not eat that much. My son was maybe pushing 6 oz per feeding by the time he was a year. Prior to that he was getting probably 4 oz bottles at each feeding. Breastfed babies do not take as much milk in their bottles as formula fed babies. Do NOT supplement your child based on your peds information.
I would start off sending 3 4oz bottles if that seems to be how much you are making each day. 4 oz might even be alot for a baby that young. Your ped is obviously not educated on breastfeeding....not really a surprise, most aren't. If you really want to check how much she normally takes, if you can go to an LC and weigh your daughter prior to nursing, and then after nursing, that will tell you how much milk she took in, which will give you an idea as to how much to put in her bottles.
When my son was young and in daycare, I had a home daycare, and I just gave her an extra bag of frozen milk, which she kept in her freezer. I had her keep it for about 3 months, then I would get it from her one day and take it home and thaw in the fridge to use to make bottles for that day, then I would freeze some of the fresh milk and just trade it out. It really helps alot if you pump before returning to work in order to have some "back up" milk in the freezer for those occasions when you don't quite make enough one day, or just in general for emergency use. You could send 3 bottles each day and a small can of formula and instruct them not to use it unless she had already taken the 3 bottles you prepare and is still hungry. Or you can take an extra bag that is frozen, then if it isn't used that day, just take home and put in the fridge and use for the next day's bottles. Your supply sounds right on track. You may suggest to them at daycare that she may need to eat less at more frequent intervals rather than 3 big feedings. They should be familiar with breastfed babies and if they are not I would look at other daycares.
Read this article for more info http://www.kellymom.com/bf/pumping/pumping_decrease.html
Good luck! Pumping and working is hard to do and a big commitment. Congratulations on doing such a great thing for your little girl!!