S., do not, DO NOT, put cereal in your newborn's bottle. PLEASE do not put cereal in your newborn's bottle. She doesn't need cereal. Her body can't digest cereal yet. This practice, which started around the beginning of the 20th Century, has led to colic and childhood obesity. Your baby's body needs milk fat and protein; cereal is almost 100% carbohydrates, which is like feeding her candy. Even though it is a trick to get babies to sleep longer between feedings, it is a huge injustice to your baby's digestive system.
She sounds like she is eating just fine. When she gets a growth spurt, she will eat more, and when her body isn't growing as much, she will eat less. If she only eats when she's hungry, that's a good thing. Don't disrupt her feeding cycles. Don't try to get her to go longer between feedings at this stage. Babies whose digestive systems are tricked this way are actually malnourished in a way because their metabolisms are being messed with. If a baby needs to eat every 2-4 hours, it's because her body needs the fuel and nutrients.
Please, PLEASE don't put cereal in her bottle.
Peace,
Syl