[wanna be a young mother]

Nevaeh is eating 4oz (120cc) a feeding now. She eats about 6-7 times a day. (6:00am, 9:00am, 12:00pm, 3:00pm, 6:00pm, 9:30pm, 2:00am) During the day she goes about 3 hrs between feedings and at night she goes about 4-4.5hrs. If I give her 3oz she scream 1-2hrs later to eat. So I started giving her 4oz and she takes it fine but my mom keeps saying that is WAY TO MUCH to give her in a feeding. Nevy is over 8lbs now and does fine on the new formula. Am I feeding her too much? I know they say to let your baby eat on demand but is that too much food for her? If it is then how do I get her to eat less? If she eats less than 4oz she crys and eats her fingers until I give her more food. She doesn't really throw up as much as she use to since I've been giving her the 4oz. I am just lost on what to do. How can you tell the baby is eating to much formula? She has a Dr. appt next week so I will ask her Ped but I thought I would see what everyone else has to say first.