can you over feed a newborn? (11 weeks old)

I just feed her formula when she's hungry so about 4oz every 2-3 hours and sometimes in between if she's still hungry, which I thought was normal but her cousin who is 3 months older doesn't eat as often as that. She is a big girl, 26 in long and 13 lbs but she's not unhealthy according to her doctor. So what do you think?