Hi S.,
Please do not, as another poster suggested, try to give your baby milk. No pediatric expert would suggest this. Regular milk does not have the nutrients that babies need. The only things recommended for infants are mothers milk or formula. A desperately hungry baby will not decline their formula due to taste (remember, this isn't a drink for them, it is their food) and will be hysterical if they are hungry. While you didn't mention this in your post, I'm wondering if you've started feeding solid foods. Remember that solids are not recommended til six months and in the first year, should never take the place of breastmilk or formula feedings - your baby gets their nutrition from that liquid and very little nutrition from those baby foods. Solids should only be given after their milk feeding and if it's drastically cutting down on their consumption of breastmilk or formula, I would discontinue the food.
I think it's best to determine what your baby is taking in over the course of a whole day rather than an individual feeding. Has she always been this way? Is she continuing to have plenty of output in her diapers, gaining weight steadily and hitting all developmental milestones in the normal range? If she is doing all of these things, then it is likely that she is getting the nutrition that she needs.