How can 1/2 oz of food make such a difference?

An old story that is new to me.

Let's imagine that it's 8 PM and Violet is beginning her "I'm hungry" chirping and wiggling. In this imaginary situation let's further pretend that I warm up some milk and begin feeding the bottle. Joanna was in the shower and I thought I would be helpful by feeding the critter and giving her a break. Our feeding was uneventful enough she took about 3 oz of food in 20 minutes. After she finished the bottle she slept for about 17 minutes and woke up REALLY pissed off.

I'm thinking, "Man, she just ate a huge amount of food, she probably has some gas, or needs to drop a load, or burp." Suffice it to say I was under the impression that this would soon pass and she would calm down. Nothing doing, she oscillated between fussy and pissy for 45 minutes until I finally gave up and offered her some more food. Less than 1/2 oz of food later she was asleep. And not just a little bit asleep. I'm talking baby coma. The kind of sleep that makes you think that you might be able to get some sleep of your own.

It's tough for me because I don't want to misdiagnose discomfort as hunger and just give her food any time she makes a fuss. On the other hand, she won't fall asleep until her tank is full. Like I said, I'm guessing that every parent has to figure out how to read their kid, and we are no different. Violet is a complicated woman.