If she's sleeping 3 hours afterwards it means she's eating enough to fill her teeny tiny belly, otherwise she'd wake agitated for more food.

Babies tummies at this age are teeny tiny so they can't take a lot of food so that's about the right amount of time to feed, plus every baby is different and some babies are more efficient at getting milk out than others. Best indicator of how much they are getting is their wet and dirty nappies :) xx

That's about perfect, she is doing it by the book