Bottle fed babies

My girl is 9 weeks will be 10 on Friday and she’s formula fed. We tried breast feeding but had great complications and now I have no supply. She’s been on formula since 2 weeks starting out just supplementing and now obviously fully formula fed. My question is how much should she be eating? I think she’s starting to go through a bit of a sleep regression. But she’s also eating a LOT more. Anywhere from 6-9oz. But then when she’s tired during the day it’s a struggle to get her to even eat 4oz. Any suggestions? Or do I just keep doing what I’m doing?