Your baby is the boss of the breast - as she's the one who controls how fast (or slow) she feeds. Babies are able to extract milk from their mother's breast, and they have the power to make the milk stop flowing. Just by stopping the peristaltic motion and suckling action.
Babies naturally - and very precisely - coordinate between suckling, swallowing and breathing. A sign that baby is actively drinking can be heard as she rhythmically grunts or gulps. But what's going on inside her mouth?
After every swallow of mother's milk, baby takes a quick breath - then suckles again. This rhythm of drink-swallow-breathe repeats until baby stops altogether, to take a break and just breathe. Then it's time to start feeding again, until baby's belly is full and feeding time is over.