breastfeeding and bottles

My 10w daughter just started going to my husbands aunt last week so I could go back to work. I'm pumping 3 times at work so I can provide bottles to her for feeding. I average 14-16oz through the day over 6 bottles, the first 2 in the morning are always larger with the last 4 being almost exactly 2oz each. Since I can only pump 2oz at a time, I was giving her 4 2oz bottles for the day as my daughter eats consistently every 1.5 hours. She told me that when she drank 2oz she would scream, but if she gave her 3oz (I gave her a stock pile) she was fine. I'm torn because my daughter has no problem breastfeeding and if I only produce 2oz, why does she want 3oz from a bottle?  Help