Ah, at 2 weeks old, 3oz every 3 hours is actually quite normal lah, newborns need to eat frequently because their tummies are so kecil! The fact that she's still hungry after breastfeeding suggests your supply might still be building (which is totally normal at this stage), so the formula top-up is actually helping her get enough. A few of us went through the same thing, my midwife told me to keep doing the breast first then formula, and the more baby feeds, the more milk will come in, so don't stress. That said, it's worth checking with your doctor or lactation consultant to make sure baby's weight is on track and get tips on maximizing your milk production, they can also confirm if the amounts she's taking are right for her.