If she's still hungry up it 2 ozs. You may find she takes more at one point and then less at a different time. As others said you don't have to feed every 3 hours, just feed on demand.
Everytime they polish of an ounce, add another one, make 2oz she might drink one and a tiny bit or one and a half, when she starts finishing the full 2 then make 3 and so on. Also doesn’t have to be 3 hrs just feed on demand, as and when she wants it x