My 2 month old eat 4oz of pumped breast milk every 3 hours and sometimes still wants to eat more. Sometimes she will eat an oz of formula & be ok?

Breastmilk v formula. Breastmilk is definitely healthiest, but if baby seems hungry all the time, are you getting enough nutrition in, to pass along to her? Your milk may be thin if you're not eating enough yourself, or if you're very stressed & exhausted as new moms can be! it's okay to supplement with some formula for her satiety, but also make sure you're doing enough to take care of you so you can take care of her.
FEEDING. It is called self demand feedings. Sometimes she is hungry and consumes several oz of milk. Occasionally, feedings are less due to her mood.