All babies eat different amounts and at different time intervals. We all have our methods of how we would like to feed our babies. I personally took the On Demand approach.
One thing to consider/question for you: Does she spit up a lot during or after feeding? If so, it's possible she's eating too fast or not burping enough in between. Therefore she needs to feed sooner as well as looking like she eats more than other babies.
Oh do I hear you. Honestly...there is not much you can do to hold her off. Not every baby waits the three hours. My little guy was breastfed and ate every hour to hour and a half for the first few months. It was hard, but we got through it. Some babies just need to eat more frequently. I have to say though..4 to 5 oz per feeding at her age is awesome! It does sound like she may be on a growth spurt. Has it been this way since the beginning?
Are you breastfeeding? If you are, she should be able to eat on demand.
If you are bottle feeding, it sounds like she's going through a growth spurt. Is she overweight?